PHYSICAL REVIEW B 93, 205108 (2016)
High- esolu ion Mn K-edge x- ay emission and abso p ion spec oscopy s udy o he elec onic
and local s uc u e o he h ee di e en phases in Nd0.5S 0.5MnO3
S. La ue za,1,*J. Ga c´
ıa,2G. Sub´
ıas,2J. Blasco,2and P. Gla zel1
1ESRF-The Eu opean Synch o on, 71, A enue des Ma y s, G enoble, F ance
2Ins i u o de Ciencia de Ma e iales de A ag´
on, Depa amen o de F´
ısica de la Ma e ia Condensada,
CSIC-Uni e sidad de Za agoza, C/ Ped o Ce buna 12, 50009 Za agoza, Spain
(Recei ed 4 Ma ch 2016; e ised manusc ip ecei ed 11 Ap il 2016; published 9 May 2016)
Nd0.5S 0.5MnO3is pa icula ly ep esen a i e o mixed- alen mangani es since hei h ee cha ac e is ic
mac oscopic phases (cha ge-o de ed insula o , e omagne ic-me allic, and pa amagne ic insula o ) appea a
di e en empe a u es. We he e epo a comple e x- ay emission and abso p ion spec oscopy (XES-XAS) s udy
o Nd0.5S 0.5MnO3as a unc ion o empe a u e o in es iga e he elec onic and local s uc u e changes o he
Mn a om in hese h ee phases. Compa ed wi h he di e ences in he XES-XAS spec a be ween Nd0.5S 0.5MnO3
and he single- alen e e ence compounds NdMnO3(Mn3+)andS /CaMnO
3(Mn4+), only modes changes ha e
been ob ained ac oss he magne oelec ical ansi ions. The XES spec a, including bo h he Mn Kαand Kβ
emission lines, ha e mainly shown a sub le dec ease in he local spin densi y accompanying he passage o he
e omagne ic-me allic phase. Fo he same phase, he small in ensi y a ia ions in he p e-edge egion o he
high- esolu ion XAS spec a e lec an inc ease o he p-dmixing. The analysis o hese XAS spec a imply
a cha ge seg ega ion be ween he wo di e en Mn si es a om one elec on, being in in e media e alences
Mn+3.5±δ/2(δ<0.2e−) o all he phases. Ou esul s indica e ha he spin, cha ge, and geome ical s uc u e o
he Mn a om ha dly change among he h ee mac oscopic phases demons a ing he s ong compe i ion be ween
he e omagne ic conduc o and he cha ge-o de ed insula o beha io s in he mangani es.
DOI: 10.1103/PhysRe B.93.205108
I. INTRODUCTION
Mixed- alen manganese pe o ski es o he ype
RE1−xAxMnO3,RE
1−xA1+xMnO4, and RE2−2xA1+2xMn2O7
(RE = a e-ea h, A=alkaline-ea h), he ea e e e ed o as
mangani es, ha e ecen ly been he subjec o an ex ensi e and
deep s udy due o he occu ence o exo ic phenomena like
colossal magne o esis ance o so-called cha ge o de ing (CO)
[1–4]. Despi e his b oad in e es , a comple e and comp ehen-
si e unde s anding o he changes in he Mn local elec onic
s uc u e along wi h he complex beha io exhibi ed by hese
mangani es is lacking. Depending on he o mal alence s a e
o he Mn a om, hey show di e en magne ic and elec ical
phases (including e omagne ic-me al o an i e omagne ic-
insula o ) and also phases iden i ied as cha ge-o bi al o de ed.
The classical desc ip ion o his beha io in e ms o ionic
Mn3+/Mn4+con igu a ions which includes he double ex-
change mechanism has been challenged by bo h expe imen al
esul s and elec onic s uc u e calcula ions [5–11].
Among hem, hal -doped mangani es wi h gene al o mula
(RE0.5A0.5)MnO3p esen many in iguing ea u es such as
eal space o de ing o cha ge, spon aneous phase sepa a ion,
ield-induced an i e omagne ic-insula ing o e omagne ic-
me allic ansi ion esul ing in a gian change in esis i i y,
e c. [4]COo Mn
3+/Mn4+and o bi al o de ing was p oposed
as he inge p in o he cha ge exchange an i e omagne ic-
insula ing low empe a u e phase [12–20]. The con en ional
model used o desc ibe his low- empe a u e phase is a one-
dimensional zigzag chain o Mn a oms in he ab plane coupled
an i e omagne ically o each o he wi h a checke boa d
o de ing o he Jahn-Telle dis o ed Mn3+and iso opic Mn4+
*[email p o ec ed]
ions. In pa icula , Nd0.5S 0.5MnO3is e y ep esen a i e
since he h ee mac oscopic phases o hal -doped mangan-
i es (cha ge o de ed insula o , e omagne ic conduc o , and
pa amagne ic insula o ) appea a di e en empe a u es [21].
Abo e he e omagne ic o de ing empe a u e TC=255 K i
is a pa amagne ic insula o , in he ange 255 K ⩾T⩾150 K
i is a magne o esis i e e omagne ic me al, and below he
an i e omagne ic o de ing empe a u e TN=150 K i shows
CO. In sho , he p oposed mechanism o he phase ansi ions
has been explained as ollows: In he pa amagne ic phase, he
doped holes a e andomly localized a he Mn si es being he
luc ua ion ime among he si es la ge han he pe manence
ime a each si e. Then he e omagne ic-me al phase is
assumed o appea due o he double exchange mechanism and
he doped holes a e highly delocalized and sp ead ou o e he
Mn a oms. Finally, he insula o CO phase is desc ibed as he
spa ial localiza ion o he doped holes wi h a pe iodic o de ing
o Mn3+and Mn4+ions.
X- ay abso p ion measu emen s a he Mn Kedge in
he La1−xCaxMnO3se ies ha e demons a ed he absence
o in ege ionic s a es o he Mn a oms [6,8,9,22–25]. In
addi ion, esul s o esonan x- ay sca e ing (RXS) a he
Mn Kedge in hal -doped mangani es ha e shown ha he
elec onic disp opo iona ion be ween he di e en si es in he
checke boa d Mn o de ing is o he o de o 0.2 elec ons
[5,26–30]. On he o he hand, ex ended x- ay abso p ion ine
s uc u e (EXAFS) da a in La1−x(Ca,S )xMnO3compounds
ha e p o en ha he local s uc u e a ound he Mn a om is
dis o ed in bo h he cha ge-o de ed and pa amagne ic phases,
whe eas he e omagne ic-me allic phase appea s concomi-
an ly wi h a collapse o his dis ibu ion in o a symme ic
en i onmen o he nea es -neighbo ing O a oms [6,31–33].
We he e p esen a comple e s udy o he local elec onic
and geome ical s uc u e o he Mn a om in he h ee di e en
2469-9950/2016/93(20)/205108(11) 205108-1 ©2016 Ame ican Physical Socie y
S. LAFUERZA e al. PHYSICAL REVIEW B 93, 205108 (2016)
phases o Nd0.5S 0.5MnO3by high- esolu ion x- ay emission
and abso p ion spec oscopy (XES-XAS) [34–37]. The de ec-
ion o he emi ed x- ays a e Kedge pho on abso p ion as
a unc ion o bo h inciden and emi ed ene gies makes he
high- esolu ion XES-XAS echniques unique o de ec small
elec onic and/o geome ical di e ences among he di e en
phases. Like XAS, XES is also sensi i e o he oxida ion s a e
o he Mn a oms bu i has he ad an age ha i is less dependen
on he ligand en i onmen . We ha e eco ded XES a bo h he
Mn Kαand Kβlines. The Kαlines a e he s onges luo es-
cence lines and a ise om 2p o 1s ansi ions; while abou 8
imes weake a e he co e- o-co e (CTC) Kβlines, which esul
om 3p→1s ansi ions; and again 50–100 imes weake a e
he alence- o-co e (VTC) Kβlines which a e ansi ions om
he alence shell o he 1ss a e [35]. We also pe o med high-
ene gy esolu ion luo escence-de ec ed (HERFD) abso p ion
spec oscopy by se ing he emission ene gy o he maxima
o he main luo escence lines and eco ding he in ensi y as a
unc ion o he ene gy o he inciden pho ons ac oss he Mn K
edge. Fo he sake o compa ison, he same measu emen s we e
ca ied ou in pa allel on he ela ed single- alen compounds:
NdMnO3(Mn3+), S MnO3(Mn4+), and CaMnO3(Mn4+).
NdMnO3and CaMnO3unde go an i e omagne ic ansi ions
a a TNo abou 78 K [38] and 125 K [39], espec i ely, whe eas
cubic S MnO3adop s an an i e omagne ic s uc u e be ween
230 and 260 K depending on he oxygen s oichiome y o he
samples [40–41].
We no e ha because o he in e e ence be ween he
Mn Kedge and he Nd L2edge, o Nd0.5S 0.5MnO3 he
EXAFS signal canno be ob ained by means o s anda d XAS.
In e es ingly, we ha e been able o wo k ou he EXAFS
spec a o his compound by using he simul aneously eco ded
o al luo escence and high- esolu ion da a measu ed a he
maximum o he Kα1emission line. In his way, he empe a-
u e dependence o he EXAFS signal ac oss he h ee di e en
phases o Nd0.5S 0.5MnO3has also been cha ac e ized.
Ou esul s show ha he elec onic s a e o he Mn a om
in Nd0.5S 0.5MnO3is in e media e be ween he single- alen
compounds and changes e y li le in he h ee phases:
pa amagne ic-insula o , e omagne ic-me al, and an i e o-
magne ic cha ge-o de ed. The simila i y o he Mn elec onic
and local s uc u al s a e a he di e en magne oelec i-
cal phases explains he s ong compe i ion be ween he
e omagne ic-me allic and he CO phases in his compound
and by ex ension in he mangani es.
II. EXPERIMENTAL
Polyc ys alline samples o Nd0.5S 0.5MnO3,NdMnO
3,
S MnO3, and CaMnO3we e syn hesized using a sol-gel
me hod by he ci a e ou e. De ails abou he syn hesis a e
gi en in Re s. [42,43]. The ob ained specimens we e single
phase as con i med by con en ional x- ay powde di ac ion.
Magne ic measu emen s we e also pe o med be ween 5
and 300 K using a comme cial supe conduc ing quan um
in e e ence de ice (SQUID) magne ome e . Acco ding o he
magne ic suscep ibili y measu emen s, Nd0.5S 0.5MnO3shows
wo phase ansi ions a TC≈255 K and a TN≈150 K [5].
The expe imen was pe o med a ID26 beamline o he
Eu opean Synch o on Radia ion Facili y (ESRF) in G enoble
(F ance). The inciden ene gy was uned h ough he Mn K
edge by means o a pai o c yogenically cooled Si(311)
monoch oma o c ys als. Rejec ion o highe ha monics was
achie ed by h ee Si mi o s wo king unde o al e lec ion
(2.5 m ad). A e e ence Mn me allic oil was used o calib a e
he monoch oma o ene gy by se ing he i s in lec ion
poin o he Mn Kedge a 6539 eV. The inelas ically
sca e ed pho ons we e analyzed using a se o ou sphe ically
ben Ge(333) and Ge(440) c ys als o he Mn Kαand
Kβlines, espec i ely. The analyze c ys als we e a anged
wi h he sample and de ec o (a alanche pho odiode) in a
e ical Rowland geome y (R≈1 m). The o al expe imen al
b oadening, de e mined as he a e age o he ull wid h a hal
maximum (FWHM) o he elas ic p o iles, was abou 0.4 eV
(Mn Kα) and 0.7 eV (Mn Kβ). Non esonan Mn Kαand
KβXES scans we e eco ded a inciden ene gy o 6700 eV.
HERFD-XAS spec a a he Mn Kedge we e measu ed a
a ious emission ene gies while eco ding simul aneously he
o al luo escence yield (TFY) wi h a diode. X- ay abso p ion
nea edge s uc u e (XANES) spec a we e collec ed o all he
samples a he maximum o he Mn Kα1emission line while
EXAFS spec a we e only measu ed in Nd0.5S 0.5MnO3. Spin-
selec i e XANES spec a we e measu ed a he maximum
o heMnKβ1,3emission line o each sample and also
a he maximum o he Mn Kβshoulde . A con inuous
He- low c yos a was used o he empe a u e-dependen
measu emen s. The da a we e collec ed on concen a ed pelle s
a e inding no di e ence in he XANES spec a as compa ed
wi h 5 −10% in mass dilu ed pelle s. Sel -abso p ion e ec s
can be disca ded as almos no di e ence is ound be ween
XANES spec a eco ded in TFY mode and hose measu ed
in ansmission mode wi h op imal hickness o ge a jump a
he edge o abou 1.
The applied da a ea men p ocedu es a e desc ibed in he
ollowing. The XES spec a ha e been no malized wi h espec
o he a ea using he ange 5876–5908 eV o he Mn KαXES
and he ange 6461–6506 eV o he Mn KβXES. The Mn Kα
XES spec a ha e been i ed wi h wo Lo en zian unc ions
o de e mine he FWHM o he Kα1line [44]. The Mn Kβ
VTC egion spec a ha e been u he ea ed by pe o ming a
backg ound sub ac ion in o de o ge id o he con ibu ion
om he CTC main line ail. Fo ha , we ha e modelled he
backg ound using se en Voig unc ions ha ha e been i ed
o se e al da a poin s below (6492–6515 eV) and abo e (6540–
6565 eV) he VTC ea u es ollowing he p ocedu e desc ibed
in Re . [45]. Rega ding he x- ay abso p ion da a, he XANES
spec a ha e been no malized o he high-ene gy pa well
abo e he abso p ion edge (abou 100 eV) [46]. The Fou ie
ans o ms (FTs) o he EXAFS signals we e calcula ed o
ak ange o 1.5–12 ˚
A−1usingasinewindow.TheEXAFS
s uc u al analysis has been pe o med using heo e ical phases
and ampli udes calcula ed by he FEFF-6 code [47] and i s o
he expe imen al da a we e ca ied ou in R space wi h he
ARTEMIS p og amme o he Deme e package [48].
III. RESULTS
A. Mn Kαand KβXES spec a
Figu e 1compa es he Mn KαXES spec a o
Nd0.5S 0.5MnO3,NdMnO
3(Mn3+), S MnO3(Mn4+), and
205108-2
HIGH-RESOLUTION Mn K-EDGE X-RAY EMISSION . . . PHYSICAL REVIEW B 93, 205108 (2016)
FIG. 1. No malized Mn KαXES spec a o Nd0.5S 0.5MnO3,
NdMnO3,S MnO
3,andCaMnO
3measu ed a 80 K. Inse : Kα1
line ull wid h a hal maximum (FWHM) om he same da a as
a unc ion o o mal alence. The ed line is a linea i conside ing
only NdMnO3and S MnO3.
CaMnO3(Mn4+) measu ed a 80 K. These spec a consis
o wo peaks, Kα1and Kα2, which co espond o 2p3/2and
2p1/2 inal s a es, espec i ely. We no e ha he maximum o
he Kα1peak is shi ed o highe ene gies by abou 0.2 eV
o he Mn3+compound compa ed o he Mn4+samples while
he spec um o mixed- alen Nd0.5S 0.5MnO3lies close o
ha o NdMnO3. Clea ly, he KαXES o Nd0.5S 0.5MnO3
canno be desc ibed by a 1:1 supe posi ion o he spec a o
NdMnO3and S MnO3. We ha e i ed he spec um using
he o mula σNd0.5S 0.5MnO3=(1 −x)σNdMnO3+xσS MnO3and
we ha e ound he bes i o he addi ion 0.8σNdMnO3+
0.2σS MnO3. The e o e, he weigh needed in he spec a is
no simply equal o he doping concen a ion. As epo ed in
p e ious wo ks [35,44,49], he Kα1FWHM can be ela ed
o he spin s a e. The inse o Fig. 1shows he e olu ion o
he Kα1line FWHM o he ou compounds plo ed e sus
o mal alence. We no e ha he alue co esponding o
Nd0.5S 0.5MnO3 alls ou om he linea dependence be ween
hese wo pa ame e s conside ing he single- alen compounds
and appea s nea e o he one o NdMnO3.
We con inue wi h he Mn CTC KβXES spec a o he
same samples measu ed a oom empe a u e (RT), which a e
shown in Fig. 2. In his case, he spec al ea u es a ise om a
3p→1sdecay p ocess and a e sepa a ed in o he s ong Kβ1,3
peak and a b oad Kβshoulde a lowe emi ed ene gy. The
p esence o he Kβsa elli e and he ene gy spli ing be ween
he Kβ1,3and Kβlines a e de e mined by he in a-a omic
exchange in e ac ion be ween he spin o he 3phole and he
3delec ons. The s ong Kβ1,3peak (low in ense Kβshoulde )
is mainly a ising om he coupling be ween he 3phole, which
is an ipa allel (pa allel) o he o al spin o he 3delec ons. In
his way, compounds wi h he same spin s a e show e y simila
spec a as obse ed o ou samples wi h o mal Mn4+(3d3)
ionic s a es. Ne e heless, sys ema ic changes wi h Mn alence
when inc easing om 3+ o 4+a e obse ed. The Mn alence
FIG. 2. No malized Mn CTC KβXES spec a o
Nd0.5S 0.5MnO3, NdMnO3,S MnO
3,andCaMnO
3measu ed
a RT. Inse : Fo mal spin alues de i ed om he IAD analysis o
he same da a as desc ibed in he ex plo ed e sus o mal alence.
E o ba s ha e been es ima ed by compa ison wi h he da a poin s
o he wo bina y oxides and he solid line is he linea dependence
conside ing he la e poin s.
inc ease is e lec ed in he shi o he Kβ1,3maximum o lowe
ene gy (∼0.4 eV) and s ong b oadening on i s low-ene gy
side, and he in ensi y loss o he Kβshoulde . On he o he
hand, he spec um o Nd0.5S 0.5MnO3lies in be ween he
Mn3+and Mn4+g oups bu close o he spec um o he Mn3+
sample as ound in he KαXES spec a. In his case, he bes
ag eemen is ound o he addi ion 0.7σNdMnO3+0.3σS MnO3.
Tyson e al. [8] also epo ed a nonlinea dependence be ween
he mix weigh s and he doping concen a ion in he Mn CTC
KβXES da a o he ela ed sys em La1−xCaxMnO3 o x<
0.4, being he weigh s o x=0.3 such ha 0.9σLaMnO3+
0.1σCaMnO3. Besides, we ha e analyzed he Mn CTC KβXES
spec a using he in eg a ed absolu e di e ence (IAD) me hod
[49] in o de o e ie e he e olu ion o he Mn local spin
momen bo h ac oss he di e en compounds and as a unc ion
o empe a u e. This me hod allows quan i a i ely ob aining
he ela i e change in he local 3dspin magne ic momen by
in eg a ing he absolu e alue o he di e ence be ween sample
spec um and a e e ence spec um. In his analysis, we ha e
also included he da a o he bina y oxides Mn2O3(Mn3+)
and MnO2(Mn4+) and he la e compound has been used as
e e ence. In o de o ob ain a linea ela ionship be ween IAD
and spin (S), we ha e assumed an ionic pic u e o MnO2and
Mn2O3and used hei o mal spin alues which a e S=3/2
and S=2, espec i ely since Mn is in high-spin con igu a ion.
The inse o Fig. 2shows he o mal spin ob ained in his
way plo ed e sus o mal alence o all he compounds. The
o mal spin s a e o Mn in Nd0.5S 0.5MnO3is in e media e
be ween he single- alen samples bu i de ia es om he
co esponding a e age spin s a e in ag eemen wi h he 0.7:0.3
a io o he NdMnO3/S MnO3weigh s p e iously ob ained.
In Fig. 3a e shown he spec a o Nd0.5S 0.5MnO3measu ed
a empe a u es co esponding o he h ee phases (300 K,
205108-3
S. LAFUERZA e al. PHYSICAL REVIEW B 93, 205108 (2016)
6470 6480 6490 6500
0
20
40
60
80
100
120
140 Nd
0.5
S
0.5
MnO
3
[T=300K]-[T=200K]
[T=200K]-[T=80K]
Emi ed Ene gy (eV)
No m. In ensi y (a b. uni s)
-6
-4
-2
0
2
4
6
K
K '
T = 300 K
T = 200 K
T = 80 K
Di e ence (a b. uni s)
FIG. 3. Compa ison be ween he no malized Mn CTC KβXES
spec a o Nd0.5S 0.5MnO3measu ed a 300 K, 200 K, and 80 K (le
axis) and di e ences be ween he same spec a ( igh axis).
200 K, and 80 K). Despi e he signi ican changes in he
mac oscopic p ope ies, hese spec a a e almos iden ical (see
also he co esponding IAD alues in he inse o Fig. 2),
indica ing ha he elec onic s a es a he Mn a om a e e y
simila o he h ee di e en phases. The di e ence spec a o
Nd0.5S 0.5MnO3 o med by sub ac ing he da a a wo empe -
a u es a e also displayed. The di e ences [T=300 K]-[T=
200 K] and [T=200 K]-[T=80 K] e lec he changes ha
ake place when en e ing he e omagne ic-me allic and an-
i e omagne ic cha ge-o de ed phases, espec i ely. We ind
small bu clea ly pe cep ible changes and he signs o he di e -
ence signals a e e e sed. No changes a e obse ed in he di -
e ence [T=300 K]-[T=80 K] and he spec a o NdMnO3,
S MnO3, and CaMnO3measu ed a 80 K a e also alike he da a
a 300 K (no shown). Simila ly o Qian e al. [50] and He e o-
Ma ´
ın e al. [51], we ha e also e alua ed he di e ence
signal esul ing om a change in he Mn o mal alence
s a e by doing σS /CaMnO3–σNdMnO3,σNd0.5S 0.5MnO3–σNdMnO3, and
σMnO2–σMn2O3. Howe e , he spec al changes induced by a
Mn o mal alence inc ease do no esemble hose in he
di e ences [T=300 K]-[T=200 K] and [T=200 K]-[T=
80 K]. The obse ed he mal beha io could hus be in e p e ed
as a change in he local spin densi y be ween he e omagne ic
phase and he pa amagne ic and an i e omagne ic phases. In
o de o disce n whe he his change co esponds o ei he
an inc ease o dec ease o he local spin densi y, we ha e
compu ed he i s momen (E=j(EjIj)/jIj)o he
Kβ1,3peak in he spec a a he di e en empe a u es using he
a ea 6485–6495 eV. While his me hod is less obus o de ec
small changes han he IAD alues, i has he ad an age ha i
main ains he sign o he shi (which is los in he IAD analy-
sis). We ob ain Eequal o 6489.81 and 6489.82 eV o 300 K
and 80 K, espec i ely, and E=6489.80 eV o 200 K. Since
he spin s a e and he i s momen o he Kβ1,3peak shi in
a linea ashion as shown p e iously o o he Mn compounds
[35], we can hen conclude ha ou Mn CTC KβXES spec a
o Nd0.5S 0.5MnO3as a unc ion o empe a u e e lec a sub le
dec ease o he local spin densi y in he e omagne ic-me allic
phase as expec ed om he cha ge delocaliza ion.
FIG. 4. No malized Mn VTC KβXES spec a o
Nd0.5S 0.5MnO3, NdMnO3,S MnO
3,andCaMnO
3measu ed
a RT a e backg ound emo al.
While he CTC Kβemission lines a e sensi i e o he local
magne ic momen , VTC Kβemission lines mainly p obe he
occupied me al p-densi y o s a es (DOS) up o 25 eV below
he Fe mi ene gy. The x- ay emission p ocess is domina ed
by dipole ansi ions and he e o e he spec al ea u es
co espond o alence band s a es wi h me al psymme y.
Since he me al p-DOS is s ongly mixed wi h ligand o bi als,
he in ensi ies o he wo obse ed ea u es, Kβ shoulde and
Kβ2,5line, e lec he amoun o hyb idiza ion be ween he
me al poccupied elec onic le els and ligand sand po bi als,
espec i ely [45]. Figu e 4shows he VTC KβXES spec a
o all he samples aken a RT a e backg ound emo al. The
compounds wi h highe Mn o mal alence s a e, S /CaMnO3,
show he s onges Kβ and Kβ2,5 ea u es, indica ing a la ge
hyb idiza ion as expec ed om he sho e Mn-O dis ance ( he
a e age Mn-O dis ance is 2.05 ˚
A o NdMnO
3[52] while o
S /CaMnO3is 1.90 ˚
A[31,53,54], in ag eemen wi h a la ge
ionic adii o Mn3+compa ed wi h Mn4+). As occu ed in he
case o he Mn Kαand CTC Kβemission lines, he spec um
o Nd0.5S 0.5MnO3is e y simila o ha o NdMnO3,e en
hough in his case he Kβ2,5maximum appea s sligh ly
shi ed o lowe ene gy con a y o he expec ed posi ion
om i s oxida ion s a e. A shi o 1 eV is obse ed be ween
NdMnO3and S /CaMnO3, consis en wi h he di e ence in
one oxida ion s a e uni [55]. We also measu ed he VTC Kβ
XES spec a a empe a u es co esponding o he h ee phases
in Nd0.5S 0.5MnO3and a 80 K o he o he compounds.
Howe e , he spec a do no change wi h empe a u e ou side
he expe imen al e o o any o he samples (no shown).
The main conclusion om he Mn Kαand KβXES
measu emen s is ha while signi ican changes in he elec-
onic s uc u e a e obse ed be ween he di e en e e ence
compounds, only e y small a ia ions a e de ec ed o
Nd0.5S 0.5MnO3as a unc ion o empe a u e despi e he
di e en physical p ope ies. The elec onic s a e o he Mn
a om seems o be simila in all phases and canno be desc ibed
205108-4
HIGH-RESOLUTION Mn K-EDGE X-RAY EMISSION . . . PHYSICAL REVIEW B 93, 205108 (2016)
in e ms o a 1:1 supe posi ion o Mn3+/Mn4+(nei he
empo ally no spa ially), in ag eemen wi h he homogenous
mixed- alen cha ac e o Nd0.5S 0.5MnO3. In gene al, o
all he emission spec a, Nd0.5S 0.5MnO3shows a beha io
close o NdMnO3(Mn3+) han o S /CaMnO3(Mn4+).
Howe e , we ind e y small empe a u e changes in he
XES spec a o Nd0.5S 0.5MnO3accompanying he ansi ion
o he e omagne ic-me allic phase ha a e in e p e ed as a
dec ease in he local spin densi y and a e almos comple ely
e e sed when passing o he low- empe a u e cha ge-o de ed
insula ing s a e.
B. High- esolu ion and spin-selec i e XANES spec a
Figu e 5(a) shows he compa ison be ween he TFY-
XANES and he HERFD-XANES spec a measu ed a he
maximum o he Kα1line o he Nd0.5S 0.5MnO3sample
a RT. The HERFD-XANES shows sha pe spec al ea u es
(a bo h he p e-edge s uc u e and whi e line) han he
TFY-XANES. In Fig. 5(b) he HERFD-XANES spec a a
he Kα1line a e shown o all he compounds. The spec a a e
shi ed ollowing he expec ed end wi h he o mal alence
s a e o he Mn a om [56]. The abso p ion edge appea s a a
highe ene gy o he Mn4+compounds (S /CaMnO3) and a a
lowe ene gy o NdMnO3(Mn3+). The ene gy sepa a ion, also
e e ed o as a chemical shi , is abou 3.1 eV as deduced om
he maximum o he de i a i es o he NdMnO3and S MnO3
spec a. Fo Nd0.5S 0.5MnO3, he abso p ion edge posi ion
lies in be ween he wo ex emes sugges ing an in e media e
alence. The p e-edge s uc u e also e ol es in spec al shape
and in ensi y be ween he samples [see Fig. 5(b), inse ]. The
p e-edge o S /CaMnO3exhibi s h ee ea u es: a s ong peak
a 6542 eV (a2), a weake shoulde a ound 2 eV below (a1)
and a hi d peak abou 2 eV abo e (a3). Fo bo h NdMnO3
and Nd0.5S 0.5MnO3 he p e-edge shows wo esol ed peaks
a1 and a2 o compa able in ensi ies ha a e shi ed o lowe
ene gies ela i e o hose in S /CaMnO3.
Spin-selec ed x- ay abso p ion spec oscopy s ems om he
assump ion ha he Kβ(3p→1s) x- ay emission spec um
can be sepa a ed in o wo in e nally e e enced spin-up and
spin-down pa s [34,57–59]. The spin-up and spin-down
con ibu ions e e o a pa allel and an ipa allel alignmen
espec i ely o he 3phole spin and he local 3dmomen . One
can achie e a local spin selec i i y in he Kedge abso p ion
spec a by se ing he emission ene gy o ei he he Kβ1,3main
line o ge he spin-down con ibu ion, o he Kβsa elli e
o ob ain he spin-up con ibu ion, and measu e he emi ed
pho ons as a unc ion o he inciden x- ay ene gy. Figu e 5(c)
shows he spin-selec i e XANES spec a measu ed a he Kβ1,3
(spin-down) and Kβ(spin-up) lines o Nd0.5S 0.5MnO3a
RT. The XANES a he Kβline is shi ed o lowe ene gy
by abou 0.8 eV wi h espec o he spec um measu ed a he
Kβ1,3line as deduced om he maximum o he de i a i es.
Simila esul s we e ound o he o he samples measu ed (no
shown). Mo eo e , he p epeaks in he spin-selec i e XANES
a he Kβ1,3and Kβlines show he same shi in analogy wi h
p e ious wo ks in ela ed manganese pe o ski es [58,60,61].
HERFD-XANES spec a o he di e en compounds we e
also measu ed as a unc ion o empe a u e. The de ailed
empe a u e dependence o he HERFD-XANES spec a was
FIG. 5. No malized XANES spec a a he Mn K edge measu ed
a RT. (a) Compa ison be ween he HERFD-XANES a he Kα1line
and TFY-XANES o Nd0.5S 0.5MnO3. (b) HERFD-XANES a he
Kα1line o Nd0.5S 0.5MnO3,NdMnO
3,S MnO
3,andCaMnO
3.The
inse shows an expansion o he p e-edge egion. (c) Spin-selec i e
XANES spec a measu ed a he Mn Kβ1,3(spin-down) and Kβ
(spin-up) lines o Nd0.5S 0.5MnO3.
205108-5

S. LAFUERZA e al. PHYSICAL REVIEW B 93, 205108 (2016)
FIG. 6. Di e ence HERFD-XANES da a measu ed a he Mn Kα1line o (a) Nd0.5S 0.5MnO3be ween 292 K and each T, (b) NdMnO3
be ween 260 K and each T, (c) S MnO3be ween 260 K and each T, and (d) CaMnO3be ween 260 K and each T.
ollowed be ween 292 K and 80 K (T ≈20 K) a he Kα1
emission line ene gy because o he la ge in ensi y o he
Kα1line and he consequen ly highe signal- o-noise a io.
The di e ence signal ob ained by sub ac ing he HERFD-
XANES da a a he highes empe a u e om all he da a
iles (a di e en empe a u es upon cooling down) has been
e alua ed o be e elucida e he possible changes. Figu e 6
shows he di e ence signals ob ained o Nd0.5S 0.5MnO3,
NdMnO3,S MnO
3, and CaMnO3. The main changes occu
a he p epeaks and ising edge. Rega ding he e olu ion a
he main edge, an inc ease o he slope is obse ed when
cooling down. This e ec is common o all he samples
and can be explained as due o he eezing o he he mal
ib a ions [62,63]. We no e ha he weake a ia ion occu s
o NdMnO3whe e he Mn a om is su ounded by a e agonal-
dis o ed oxygen oc ahed on which implies a less sha p ising
edge and hus obscu es he he mal ib a ions. Conce ning
he p epeaks, NdMnO3,S MnO
3, and CaMnO3exhibi a
mono onic e olu ion wi h dec easing empe a u e, whe eas in
Nd0.5S 0.5MnO3 he s uc u es in he di e ence signal show a
change o sign. An upwa d peak appea s a 6540 eV below
240 K when he pa amagne ic-insula o o e omagne ic-
me allic ansi ion occu s ha becomes downwa d below
140 K, which co esponds o he insula ing cha ge-o de ed
low empe a u e phase. Con e sely, a downwa d peak occu s
a 6542 eV (T<240 K) ha becomes upwa d below 140 K.
This esul sugges s ha he p-dhyb idiza ion inc eases in he
e omagne ic-me allic phase and dec eases in he insula ing
phase. The hyb idiza ion inc ease in he e omagne ic phase
is consis en wi h he educ ion in local spin momen de i ed
om he Mn CTC KβXES spec a.
C. EXAFS spec a
The EXAFS signal a he Mn Kedge o Nd0.5S 0.5MnO3
canno be ob ained wi h a su icien ly long ange in k o
quan i a i e analysis by con en ional XAS measu emen s due
o in e e ence wi h he Nd L2edge (6722 eV). We ha e
205108-6
HIGH-RESOLUTION Mn K-EDGE X-RAY EMISSION . . . PHYSICAL REVIEW B 93, 205108 (2016)
o e come his p oblem by combining he HERFD-EXAFS
a he Mn Kα1line wi h he simul aneously measu ed TFY-
EXAFS. We no e ha hese EXAFS spec a su e om Nd
sel -abso p ion a he L2edge ene gy which appea s as a
posi i e con ibu ion in he TFY and as a nega i e con ibu ion
in he HERFD as discussed by Bianchini e al. [64]. In Fig. 7(a)
we show ha he EXAFS signal ee o Nd sel -abso p ion can
be ob ained om he weigh ed addi ion o he HERFD and
TFY spec a. The weigh o each spec um is i ed o supp ess
he in ense Nd L2whi e line. In any case, he EXAFS signal
ee o Nd sel -abso p ion does no signi ican ly change o a
a ia ion o 5% o he weigh ed addi ion.
The hus ob ained EXAFS signals and he co esponding
FTs a e shown as a unc ion o empe a u e in Figs. 7(b)
and 7(c), espec i ely. We obse e a weak he mal dependence
o he EXAFS signal. The spec a we e i ed including he
i s (O a oms) and second shell con ibu ions (Nd and S
a oms). The analysis shows ha he Mn a om is su ounded
by six O a oms a he same dis ance, i.e., nea ly a egula
oc ahed on, wi h a ela i ely high Debye-Walle (D-W)
ac o a 292 K. The Mn-O dis ance ha dly changes wi h
empe a u e showing simply a small inc ease a he onse o
he e omagne ic-me allic phase, whe e i is also obse ed
a minimum in he D-W ac o indica ing a less dis o ed
oc ahed on [see inse o Fig. 7(c)]. These esul s show ha he
in e a omic dis ance does no ollow a no mal expansion bu
emains nea ly cons an . On he o he hand, he Debye-Walle
ac o does no ollow a s anda d he mal a ia ion (Debye
o Eins ein models) and he high alue a low empe a u es
mani es s a small s uc u al dis o ion.
IV. DISCUSSION AND CONCLUSIONS
The combina ion o high- esolu ion XES-XAS spec o-
scopies applied o he s udy o he di e en magne o-elec ical
phases in Nd0.5S 0.5MnO3has p o ided aluable in o ma ion
on he elec onic s a e and local geome y o he Mn a om.
Se e al wo ks we e epo ed ea lie on XES expe imen s in
pe o ski e mangani es [8,48,50,51,58,60,62]bu heywe e
limi ed o only one de-exci a ion channel (mainly Mn CTC
KβXES) and lack exhaus i e empe a u e dependence. Con-
e sely, ou XES s udy includes he Mn Kαand Kβemission
lines and in he la e bo h he CTC (Kβ1,3and Kβlines)
and VTC (Kβ2,5and Kβ lines) egions as a unc ion o
empe a u e. We ob ain ha he Mn KβXES spec a a e
almos iden ical in he pa amagne ic, me allic- e omagne ic,
and CO phases o Nd0.5S 0.5MnO3. This inding indica es ha
he Mn oxida ion and spin s a e a e no signi ican ly changed
by he di e en magne ic and elec ical beha io . Only modes
a ia ions a e obse ed accompanying he passage o he
e omagne ic-me allic phase when looking a he he mal
di e ence signals o he Mn CTC Kβspec a, which a e
e e sed when en e ing he cha ge-o de ed one. These changes
ag ee wi h a small dec ease o he local spin densi y in he
e omagne ic-me allic phase compa ed wi h he pa amagne ic
and an i e omagne ic insula ing phases. The absence o majo
changes seems o be con o e sial in ega ds o he CO phase
o Nd0.5S 0.5MnO3whe e he e a e wo di e en Mn si es
(con en ionally desc ibed as Mn3+and Mn4+wi hin a simple
6.46.56.66.76.86.97.07.1
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6 (a)
No m. Abso p ion (a b. uni s)
Inciden Ene gy (keV)
TFY-XAS
HERFD-XAS
57% TFY-XAS+ 43% HERFD-XAS
024681012
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
(b)
292 K
200 K
180 K
160 K
140 K
120 K
100 K
80 K
k2(k)
k (Å-1)
*
50 100 150 200 250 300
1.85
1.90
1.95
2.00
T (K)
R
Mn-O
(Å)
0.000
0.002
0.004
0.006
2
Mn-O
(Å
2
)
01234
0.0
0.5
1.0
1.5
292 K
200 K
180 K
160 K
140 K
120 K
100 K
80 K
(c)
R (Å)
Modulus o he FT
FIG. 7. EXAFS da a o Nd0.5S 0.5MnO3. (a) Compa ison be ween
he HERFD-EXAFS a he Mn Kα1, TFY-EXAFS and de i ed
co ec ed EXAFS spec um as desc ibed in he ex . (b) k2χ(k)
EXAFS signals be ween 292 K and 80 K. As e isk indica es he
posi ion o he Nd L2edge whi e line. (c) Moduli o he FTs o he
same signals. Inse : Tempe a u e dependence o he e ined Mn-O
dis ance (closed squa es, le axis) and Debye-Walle ac o (open
squa es, igh axis) de i ed he om EXAFS da a o Nd0.5S 0.5MnO3.
The dashed line indica es he onse o he e omagne ic-me allic o
an i e omagne ic-CO ansi ion.
205108-7
S. LAFUERZA e al. PHYSICAL REVIEW B 93, 205108 (2016)
ionic pic u e). We a gue ha he elec onic di e ence among
he wo si es is oo small o be de ec ed o , in o he wo ds, he
cha ge seg ega ion be ween he wo Mn si es is e y small and
hence he wo si es a e e y simila . The la ges di e ences
in he Mn Kαand KβXES da a ha e been obse ed ac oss
he di e en compounds (mixed- alen Nd0.5S 0.5MnO3and
single- alen NdMnO3,S /CaMnO
3). In all cases, he spec a
o he single- alen samples can be g ouped in wo acco ding
o he Mn o mal alence (Mn3+and Mn4+) while he spec a
o Nd0.5S 0.5MnO3show an in e media e beha io . Bo h he
Mn Kα1FWHM and Mn Kβ1,3and Kβlines posi ion and
in ensi y a io depend on he local spin. Ou esul s indica e
ha he spin alue is in ag eemen wi h he mixed- alen s a e
o he Mn a om in insic o hal -doped Nd0.5S 0.5MnO3.
We now p oceed o he discussion o he HERFD-XANES
spec a, whe e we analyze he main edge and he p epeak s uc-
u e sepa a ely. As no ed in ela ed wo ks [6,8,9,22–25,47],
he ene gy posi ion o he main edge is co ela ed wi h he
o mal alence s a e o he Mn a om. In a i s app oxima ion,
based on an ionic model, i can be s a ed ha Mn in
Nd0.5S 0.5MnO3is composed by 50% Mn3+and 50% Mn4+,
which would co espond o a o mal alence 3.5+.I his
we e he case, hen he HERFD-XANES should ag ee wi h he
1:1 addi ion o he spec a o NdMnO3and S MnO3.Thisis
jus i ied by he ac ha he main di e ence be ween XANES
spec a o compounds wi h simila local s uc u e geome y
bu di e en o mal alence s a es comes om he ene gy shi
o he main edge while he spec al shape emains la gely
unchanged [56]. Howe e , we ind ha he HERFD-XANES
spec um o Nd0.5S 0.5MnO3s ongly disag ees wi h he 1:1
linea supe posi ion o NdMnO3and S MnO3spec a keeping
hei o iginal chemical shi E =3.1 eV as shown in Fig. 8.
Since he in e ac ion ime o he Kedge pho oabso p ion
p ocess is abou 10−15 s, his inding means ha he e is nei he
spa ial no empo al dis ibu ion o pu ely ionic s a es Mn3+
and Mn4+. This esul seems o be a odds wi h he con en ional
desc ip ion o he so-called CO phase a low empe a u es in
FIG. 8. HERFD-XANES a he Mn Kα1line o Nd0.5S 0.5MnO3
a RT compa ed wi h simula ions based on 1:1 supe posi ions o
di e en e e ence spec a and E alues as desc ibed in he ex .
Inse : Expansion o he p e-edge egion.
e mso aMn
3+/Mn4+bimodal dis ibu ion. X- ay di ac ion
and RXS expe imen s ha e epo ed a checke boa d o de ing
in he CO phase wi h wo di e en Mn si es and nonin ege
alence s a es Mn(3.5±δ/2)+whe e δ=0.16 ±0.02 [5]. The
la e co esponds o E =0.6 eV as ollows om he linea
ela ionship empi ically ound be ween chemical shi and
cha ge seg ega ion [56]. In Fig. 8 wo mo e simula ions o he
Nd0.5S 0.5MnO3spec um in e ms o 1:1 addi ions ha e been
ca ied ou aking in o accoun his chemical shi alue, ei he
using he NdMnO3and S MnO3spec a (Mn3+/Mn4+)o
adding up he Nd0.5S 0.5MnO3spec um a e applying shi s
o ±E/2=0.3eV(Mn
3.42+/Mn3.58+). The la e simula ion
i s nicely he HERFD-XANES o Nd0.5S 0.5MnO3con i ming
in his way ha in he CO phase he cha ge seg ega ion is
e y small be ween he wo di e en Mn si es, which a e in
in e media e alence s a es Mn(3.5±δ/2)+as ob ained in RXS
expe imen s. Mo eo e , i is well known ha he whi e line
wid h inc eases wi h he la ice dis o ions [52]. We no e ha
o NdMnO3whe e he local s uc u e is e agonal dis o ed,
he whi e line wid h is la ge han ha o he S /CaMnO3com-
pounds wi h egula s uc u e. Fo Nd0.5S 0.5MnO3i is simila
o S /CaMnO3, indica ing ha he Mn a om is su ounded by
an almos egula oxygen oc ahed on. This esul is consis en
wi h he lack o pu e ionic Mn3+and Mn4+ alences and
co obo a es he p esence o Mn in e media e alence s a es
wi h e y small cha ge disp opo iona ion. On he o he hand,
he spin-selec i e XANES spec a measu ed a he Kβ1,3and
Kβlines a e shi ed in ene gy by abou 0.8±0.2eV o he
ou samples as deduced om he maximum o he de i a i es.
This shi a ises om he exchange spli ing whe eby he
spin-up s a es ha e lowe ene gy han he spin-down s a es
[59], being nea ly independen o he Mn o mal alence s a e.
The e olu ion ob ained in he p epeak s uc u es is mo e
di icul o in e p e . On one hand, he p epeaks ha e been
associa ed o 1s→3dquad upole ansi ions. Howe e , he
low in ensi y p edic ed o he quad upole channel indica es
ha i s con ibu ion is e y limi ed. A dipola con ibu ion o
he p epeaks has been p oposed due o he s ong hyb idiza ion
o Mn 4po bi als wi h do bi als o adjacen Mn a oms
h ough he oxygen 2po bi als by El imo e al. [65]in
LaMnO3and Joly e al. [66]inTiO
2. O e all, i seems ha
he p e-edge ea u es con ain in o ma ion on he hyb idiza ion
wi h he su ounding a oms and he spli ing o he emp y
Mn dband. As ollows om ou esul s [see inse o
Fig. 5(b)], he o al in ensi y o he p epeaks inc ease wi h
he Mn o mal alence which can be in e p e ed as due o
he enhancemen o he 3d–2p–3dco alence (Mn–O–Mn)
when going om Mn3+-NdMnO3 o Mn4+-S /CaMnO3.In
line wi h he XES esul s, he HERFD-XANES da a do
no show la ge a ia ions wi h empe a u e. Howe e , he
di e ence spec a o he HERFD-XANES measu ed a he
Kα1line e eal changes in he p e-edge egion o mixed- alen
Nd0.5S 0.5MnO3(see Fig. 6) ha e lec an inc ease o he
p-dhyb idiza ion in he e omagne ic-me allic phase. This
esul nicely connec s wi h he educ ion in he local spin
densi y deduced om he Mn CTC KβXES spec a. Figu e 9
shows he empe a u e dependence in he p epeak egion o he
spin-selec i e XANES measu ed a he Kβ1,3(spin-down) and
Kβ(spin-up) lines a 300, 200, and 80 K o all he compounds.
We i s poin ou ha he e is no empe a u e dependence
205108-8
HIGH-RESOLUTION Mn K-EDGE X-RAY EMISSION . . . PHYSICAL REVIEW B 93, 205108 (2016)
6535 6540 6545
0.0
0.2
0.4
0.6
0.8
1.0 RT
200 K
80 K
Ca
S
Nd
0.5
S
0.5
No m. Abso p ion (a b. uni s)
Inciden Ene gy (eV)
Nd
a3
a2
a1
FIG. 9. Expansion o he p e-edge egion o he empe a u e-
dependen spin-selec i e XANES spec a measu ed a he Mn Kβ1,3
(spin-down, solid lines) and Kβ(spin-up, open symbols) lines o
Nd0.5S 0.5MnO3,NdMnO
3,S MnO
3,andCaMnO
3.
o he p e-edge spin-selec i e XANES o NdMnO3down
o 80 K. This esul can be expec ed because in he s udied
empe a u e ange NdMnO3 emains pa amagne ic-insula o
(TN≈78 K) [38] and hus no changes a e p edic ed in he
alence, spin, o co alency o he Mn a oms. Ne e heless, a
signi ican empe a u e and spin dependence o he p e-edge
spec a is obse ed o Nd0.5S 0.5MnO3and S /CaMnO3.In
Nd0.5S 0.5MnO3(TC≈250 K and TN≈150 K) upon cooling
om oom empe a u e o 200 K he a2 peak in ensi y is
sligh ly educed o he spin-down channel, whe eas a s ong
enhancemen o his in ensi y occu s wi h u he cooling down
o 80 K. A dis inc dec ease o he in ensi y o he a1 peak
is also obse ed on cooling om 200 K o 80 K, p ima ily
in he spin-up channel. A simila empe a u e a ia ion o
he p e-edge s uc u e has been ound in La0.5Ca0.5MnO3
when en e ing he an i e omagne ic CO phase [60]. In he
Mn4+-compounds s udied, simila changes a e ound when
c ossing TN. Le us ocus in he ollowing on CaMnO3
(TN≈125 K [39]) as ep esen a i e example. In he spin-up
channel below 80 K, he a2 peak in ensi y inc eases while
he a3 peak in ensi y dec eases. In he spin-down channel
he empe a u e dependence o hese p e-edge s uc u es is
e e sed below 80 K. Simila ends a e seen o S MnO3
(TN≈230–260 K [40–41]), bu in his case he changes in
empe a u e occu be ween oom empe a u e and 200 K in
ag eemen wi h he highe TN. We can hen conclude ha he
main changes in he elec onic s a e o Mn a oms ac oss he
di e en magne oelec ical phases a e ela ed o changes in
he Mn 3d-O 2pco alency ha a e also in ima ely connec ed
wi h changes in he magne ic o de ing.
The EXAFS esul s on Nd0.5S 0.5MnO3ha e shown ha
he Mn a om is su ounded by six O a oms a he same
dis ance. The Mn-O in e a omic dis ance is sligh ly la ge a
he onse o he e omagne ic-me allic phase, coinciden wi h
a minimum o he D-W [see Fig. 7(c)]. As p e iously epo ed
o he La1−xCaxMnO3se ies [9], in Nd0.5S 0.5MnO3 he
MnO6oc ahed a a e dynamically dis o ed in he pa amagne ic
high- empe a u e phase. Wi h dec easing empe a u e, he
sys em ends o s abilize by dec easing he local dis o ion due
o he p esence o long- ange e omagne ic in e ac ions. Bu ,
below 170 K, when en e ing he s a ically o de ed CO phase,
his local dis o ion inc eases again and becomes empe a u e
independen ins ead o collapsing as occu s o he magne-
o esis i e mangani es [22,31]. To he gene al beha io o
hal -doped mangani es, ou EXAFS esul s in Nd0.5S 0.5MnO3
add he inding ha he local s uc u al di e ences a he Mn
a om be ween he e omagne ic-me allic and CO phases a e
also e y small.
In summa y, his XAS-XES s udy pe o med in
Nd0.5S 0.5MnO3, whe e he h ee cha ac e is ic phases o he
hole-doped mangani es a e p esen in sepa a ed empe a u e
anges, demons a es ha he local s uc u e and he elec onic
s a e a he Mn a om ha dly change among he di e en phases.
Howe e , hey clea ly di e be ween he hal -doped sys em
and he single- alen Mn3+and Mn4+pa en compounds.
In his way, he appea ance o e omagne ic-me allic and
an i e omagne ic-CO phases mus a ise om he epo ed
e y small di e ences. Simila ly, Fe Kαand KβXES mea-
su emen s epo ed no di e ences ac oss he me al-insula o
ansi ion in Fe3O4, he a che ypal CO sys em [67]. These e-
sul s impose se ious cons ain s on he heo e ical models used
o desc ibe he mechanisms esponsible o he appea ance o
magne o esis ance and CO phenomena. Con en ionally, he
heo e ical models ha desc ibe he beha io o hal -doped
mangani es adop ed he ionic pic u e ollowing he pionee
wo k o Goodenough e al. [68,69]. The la e conside s
he exis ence o Mn3+and Mn4+ions empo ally sepa a ed
bu andomly dis ibu ed in he la ice o he pa amagne ic-
insula o and e omagne ic-me allic phases and spa ially o -
de ed Mn3+and Mn4+ions in a checke boa d a angemen o
he CO phase. This simple model has been al eady ques ioned
by expe imen al XAS [5,6,8,9,22,23], RXS [27–30], and bond
alence sum analysis [70,71] esul s showing ha he Mn
elec onic and local s uc u e in he mixed- alen compounds
canno be explained in e ms o single- alen in ege s a es.
In he so-called CO phases, he cha ge disp opo iona ion
be ween he dis inc Mn si es is nea ly indisce nible. Mos
o he models a e based on he uni o mi y o he doping and
ake as a basis he desc ip ion o he elec onic s a es o he Mn
a om in an oc ahed al c ys al ield. I is, howe e , c ucial o
no e ha he s uc u e is no pe iodic in he doped oxides.
The di alen me al and he a e-ea h a oms a e andomly
dis ibu ed in such a way ha he c ys al ield a each o he Mn
a oms, and also he local alence, change om si e o si e. Fo
example, in Nd0.5S 0.5MnO3 he Mn a oms can be su ounded
by any combina ion o (8-n)Nd+nS neighbo s. I has been
expe imen ally demons a ed ha he p ope ies o di alen
me al a e-ea h o de ed compounds show a ma kedly di e en
beha io compa ed wi h he diso de ed ones [72,73]. The key
poin is ha he elec onic s a e a he Mn a om is uni o m
ac oss he c ys al, demons a ing ha a s ong elec onic
mixing occu s in he solid. The e o e, he Mn elec onic s a e
a each si e co esponds o he geome ical a e age.
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