Magneto-caloric effect in the pseudo-binary intermetallic YPrFe17 compound

1 Magne o-calo ic e ec in he pseudo-bina y in e me allic YP Fe17 compound Pablo Ál a eza, Ped o Go iaa,*, José L. Sánchez Llamaza esb, Ma ía J. Pé eza, Vic o ino F ancoc, Ma ian Rei e sd, Joze Ko áčd, Inés Puen e-O enche, Jesús A. Blancoa. aDepa amen o de Física, Uni e sidad de O iedo, Cal o So elo, s/n, 33007 O iedo, Spain bDi isión de Ma e iales A anzados, Ins i u o Po osino de In es igación Cien í ica y Tecnológica, Camino a la p esa San José 2055, CP 78216, San Luis Po osí, Mexico. cDepa amen o de Física de la Ma e ia Condensada, ICMSE-CSIC, Uni e sidad de Se illa, P.O. Box 1065, 41080 Se illa, Spain dIns i u e o Expe imen al Physics, Wa sono a 47, SK-04001 Košice, Slo akia. eIns i u e Laue Lange in, 6 ue Jules Ho owi z, 38042 G enoble, F ance *E-mail: pgo [email p o ec ed] Abs ac . We ha e syn hesized he in e me allic YP Fe17 compound by a c-mel ing. X- ay and neu on powde di ac ion show ha he c ys al s uc u e is hombohed al wi h space g oup R3m (Th2Zn17- ype). The in es iga ed compound exhibi s a b oad magne ic en opy change ΔSM (T) associa ed wi h he e o- o-pa amagne ic phase ansi ion (TC ≈ 290 K). The iso he mal |ΔSM| (≈ 2.3 J kg-1 K-1) and he ela i e cooling powe (≈ 100 J kg-1) ha e been calcula ed o applied magne ic ield changes up o 1.5 T. A single mas e cu e o ΔSM unde di e en alues o he magne ic ield change can be ob ained by a escaling o he empe a u e axis. The esul s a e compa ed and discussed in e ms o he magne o-calo ic e ec in he isos uc u al R2Fe17 (R = Y, P and Nd) bina y in e me allic alloys. Keywo ds: A. Magne ically o de ed ma e ials; C. C ys al s uc u e and symme y; D. Magne o-calo ic e ec ; E. Magne ic measu emen s 1. In oduc ion The magne o-calo ic e ec (MCE) is nowadays a subjec o conside able cu en esea ch in e es [1-3] mo i a ed by he enhanced pe o mance (e iciency, mechanical ib a ion, size, e c) and educed en i onmen al impac o e ige a ion sys ems based on his e ec compa ed wi h hose o he exis ing apou -comp ession gas echnology [4]. In his way, di e se ypes o compounds ha e been in es iga ed un il now wi h he aim o sc u inizing bo h he in ensi y and he empe a u e ange o he MCE [3, 5-7]. A magne ic ma e ial mus exhibi a la ge magne iza ion change, ΔM, a ound i s magne ic phase ansi ion in o de o display a la ge MCE esponse. F om he poin o iew o he implemen a ion o hese ma e ials in magne ic e ige a ion sys ems, ano he impo an pa ame e is he ela i e cooling powe (RCP) [8,9], which gi es a igu e o me i o how much hea could be ans e ed be ween he ho and cold ese oi s by he magne ic e ige an in an ideal he modynamic cycle. Fo ma e ials wi h second-o de phase ansi ion he peak alue o he magne ic en opy change !SM peak is smalle han ha obse ed in ma e ials wi h i s - o de magne ic phase ansi ions [1,2]. Ne e heless he lack o magne ic ield hys e esis and he la ge ope a ion empe a u e ange in ma e ials displaying a second-o de magne ic phase ansi ion gi e commonly ise o highe RCP alues [9-11]. The e o e, a comp omise be ween he magni ude o he magne ic en opy change and he RCP is manda o y o employing a magne ic ma e ial in magne ic e ige a ion applica ions. Mos ly o he cu en p o o ypes o oom empe a u e magne ic e ige a ion employ a e-ea h-based ma e ials (wi h he a e-ea h being mainly Gd) 2 [2,12]. Howe e , some Fe- ich R2Fe17 (R = Ra e Ea h) compounds ha e shown alues o RCP compa able wi h hose o Gd-based magne ic ma e ials oge he wi h a lowe cos o he main componen (Fe), easy ab ica ion p ocedu es and absence o disad an ageous hys e esis e ec s [13,14]. Wi hin he whole R2Fe17 se ies he alloys wi h R = Y, P o Nd ha e he la ges magne ic momen pe o mula uni , and he e o e he highe !SM peak alue [15], due o he collinea e omagne ic o de , and also magne ic o de ing empe a u es, TC, a ound 300 K. These ac s make hem sui able o hei use in magne ic e ige a ion as ac i e magne ic egene a i e sys ems ope a ing a ound oom empe a u e [16]. Mo eo e , he alue o TC in his 2:17 ype o compounds can be uned by mixing wo a e ea h elemen s (i.e. in he o m R2-xR'xFe17) [17], o by pa ial subs i u ion o Fe o he 3d-a om [18]. The c ys al s uc u e o he bina y in e me allic R2Fe17 compounds can be ei he o Th2Zn17- ype ( hombohed al R3m space g oup) o ligh a e-ea hs, o Th2Ni17- ype (hexagonal P63mmc space g oup) o hea y a e-ea hs [19,20]. In he case o R = Y, Gd and Tb o in pseudo-bina y in e me allic R2-xR'xFe17 alloys wi h a mix u e o wo di e en R a oms, bo h c ys al s uc u es can coexis , wi h he a e-ea hs sha ing he c ys allog aphic si es [21-24]. In he p esen wo k we ha e s udied he c ys al s uc u e o a new pseudo-bina y in e me allic YP Fe17 alloy by means o neu on and x- ay powde di ac ion, oge he wi h i s magne ic p ope ies and he magne o-calo ic e ec up o a maximum applied magne ic ield change o µ 0∆H = 1.5 T. The expe imen al esul s a e compa ed wi h hose measu ed in bina y Y2Fe17, P 2Fe17 and Nd2Fe17. 2. Expe imen al de ails and da a analysis As-cas ingo s wi h YP Fe17 nominal composi ion we e p epa ed om 99.99% pu e elemen s ( ela i e o a e ea h con en in he case o P ) by s anda d a c-mel ing echnique unde a con olled A a mosphe e. The polyc ys alline as-cas pelle s we e sealed unde acuum in qua z ampoules and u he annealed du ing one week a 1263 K. A e inishing he hea ea men he samples we e quenched di ec ly in wa e . C ys al s uc u e was de e mined a oom empe a u e (T = 290 K) by bo h x- ay (XRD) and neu on powde di ac ion (ND). XRD s udies we e pe o med in a high- esolu ion x- ay powde di ac ome e (Sei e model XRD3000) ope a ing in B agg-Ben ano geome y. The scans in 2θ we e pe o med be ween 2 and 160º wi h 0.02º s eps and coun ing imes o 20 s pe poin using Cu Kα adia ion (λ = 1.5418 Å). The ND pa e n was collec ed on he high-in ensi y D1B wo-axis powde di ac ome e a he ILL (G enoble) wi h a neu on wa eleng h o λ = 2.52 Å, 2 hou s o acquisi ion ime and an angula ange o 80º in 2 θ (in s eps o 0.2º). The ull-p o ile analysis o he di ac ion pa e ns was ca ied ou wi h he FullP o sui e package [25], and no peak b oadening due o small c ys al and/o mic os ain e ec s [26] we e de ec ed. The low-magne ic ield magne iza ion as a unc ion o empe a u e M(T) cu es we e eco ded in a Fa aday suscep ome e unde a hea ing a e o 2 K/min. Iso he mal magne iza ion cu es, M(H), we e measu ed wi h a Lakesho e model 7407 VSM ib a ing sample magne ome e in he empe a u e ange be ween 90 and 450 K wi h a maximum applied magne ic ield o 1.5 T, and in a Quan um Design MPMS-5T magne ome e in he empe a u e ange 90 – 390 K wi h applied magne ic ields up o 5 T. A each empe a u e he magne iza ion was measu ed o a la ge numbe selec ed alues o he applied magne ic ield (≈ 150 o he VSM measu emen s and 50 o he MPMS) wi h he aim o gaining accu acy in he es ima ion o he iso he mal magne ic en opy change, |∆SM|. The alue o |∆SM| a each empe a u e T due o a change o he applied magne ic ield om H = 0 o H = Hmax we e calcula ed using he Maxwell ela ion [8]: ! "SM(T,H) =SM(T,H) #SM(T,0) = $M(T',H' ) $T' % & ' ( ) * T'=T 0 H +dH' (1) 3 A e applying his p ocedu e o he whole se o M(H) cu es he alue o |ΔSM| o a gi en applied magne ic ield change and a a selec ed empe a u e is ob ained by nume ical app oxima ion o eq. 1, whe e he pa ial de i a i e is eplaced by ini e di e ences and hen he in eg al is calcula ed by means o nume ical me hods [6,9]. In addi ion, he ela i e cooling powe (RCP) has been calcula ed using h ee di e en c i e ia (see e e ence [9] o de ails): RCP-1(H) = |ΔSM max|(H) × δTFWHM(H), whe e δTFWHM is he ull wid h a hal maximum o |ΔSM|(T) cu e; RCP-2 is he a ea below |ΔSM|(T) cu e in he empe a u e ange be ween T-δTFWHM and T+δTFWHM; and RCP-3 is he maximum alue o he p oduc |ΔSM|×ΔT below he |ΔSM(T)| cu e. 3. Resul s and discussion In Fig. 1 he oom empe a u e x- ay (uppe panel) and neu on (bo om panel) powde di ac ion pa e ns o he YP Fe17 sample a e shown. 0 5 x 104 1 x 105 2 2.5 3 3.5 4 4.5 In ensi y (coun s) YP Fe17 (Neu ons) 0 1000 2000 1 1.5 2 2.5 3 3.5 In ensi y (coun s) d (Å) YP Fe17 (XRD) Fig. 1. Obse ed (do s) and calcula ed (solid line) powde di ac ion pa e ns o YP Fe17 alloy collec ed a T = 300 K. Posi ions o he B agg e lec ions a e ep esen ed by e ical ba s; he i s ow co esponds o he hombohed al Th2Zn17– ype phase while he second one is associa ed wi h an α-Fe impu i y (< 3%). The obse ed–calcula ed di e ence is depic ed a he bo om o each igu e. Bo h XRD and neu on di ac ion pa e ns ha e been e ined by using he Rie eld me hod in mul i-pa e n mode (see [25] o u he echnical de ails). The obse ed in ensi y peaks can be indexed as he B agg e lec ions co esponding o a hombohed al Th2Zn17- ype c ys al s uc u e wi h R3m space g oup (#164), and i he hexagonal se ing is chosen he la ice pa ame e s a e: a = 8.540 (1) Å and c = 12.419 (1) Å. No aces o he hexagonal Th2Ni17- ype c ys al s uc u e ha e been ound, as con i med by neu on di ac ion om which in o ma ion o he whole sample is a ained, in con as wi h XRD. Whe eas in o he 2:17 pseudo-bina y alloys o his amily a diso de ed hombohed al s uc u e has been p oposed in o de o explain he s ong in ensi y educ ion obse ed o many e lexions [27,28], in he p esen case he e is no such a educ ion, e en hough when compa ed wi h he di ac ion pa e ns o he bina y Y2Fe17, P 2Fe17 o Nd2Fe17 alloys [13,29]. F om he i o he di ac ion pa e ns i is e iden ha he 6c si e co esponding o he R a oms is equally sha ed be ween Y and P wi h he same a omic coo dina es. The alues o he 4 main c ys allog aphic pa ame e s a e gi en in Table I. The alues o he cell pa ame e s a e, as i could be expec ed, be ween hose o he Y2Fe17 and P 2Fe17 (a = 8.46 Å, c = 12.39 Å and a = 8.585 Å; c = 12.464 Å, espec i ely) [13,20,30]. The a io c/a ~ 1.54 is in good ag eemen wi h hose epo ed o he hombohed al c ys al s uc u e in hese 2:17- ype alloys [13,29,30]. In o de o es ima e he Cu ie empe a u e o he sample, he magne iza ion s. empe a u e, M(T), cu e unde a low applied magne ic ield µ 0H = 5 mT (no shown) has been measu ed. The ea e , he alue o TC has been aken as he minimum o he dM/dT s. T cu e, which is a commonly adop ed c i e ion [13,24,29]. In his way, TC = 291 ± 5 K o YP Fe17, which is in be ween hose epo ed alues o P 2Fe17 (TC = 286 ± 2 K [13]), and o Y2Fe17 (TC = 301 ± 4 K [15]). The e o e, i seems ha by mixing Y and P he Cu ie empe a u e o he esul ing pseudo-bina y alloy can be uned be ween hose alues o he pu e bina y compounds. Fig. 2 shows a 3D su ace plo ep esen ing simul aneously he empe a u e and magne ic ield dependences o he magne iza ion, M(H,T) o YP Fe17 alloy. Fig. 2. 3D su ace co esponding o he empe a u e and applied magne ic ield dependences o he magne iza ion o he YP Fe17 compound. The iso he mal magne ic en opy change, |∆SM| has been calcula ed om he se o iso he mal magne iza ion s. applied magne ic ield, M(H), cu es depic ed in Fig. 2 and ollowing he p ocedu e explained in he p e ious sec ion. In Fig. 3 he empe a u e dependence o |ΔSM| o he maximum applied magne ic ield change, om 0 o µ 0Hmax = 1.5 T is shown. In addi ion, da a o Y2Fe17, P 2Fe17 and Nd2Fe17 bina y in e me allic compounds wi h he same hombohed al Th2Zn17- ype c ys al s uc u e a e also shown o compa ison. The maximum alue o he magne ic en opy change, !SM peak , o he YP Fe17 compound is 2.3 J kg-1 K-1, which is jus in be ween hose alues o he bina y P 2Fe17 (2.6 J K-1 kg-1) and Y2Fe17 (1.9 J K-1 kg-1) alloys. The la e can be unde s ood aking in o accoun ha !SM peak is oughly p opo ional o he magne iza ion change o he alloy ac oss he second o de e o- o pa amagne ic phase ansi ion. In he case o P 2Fe17, he magne ic momen s o P and Fe subla ices a e pa allel o each o he , hence, he con ibu ion o P a oms (≈ 3 µB/P a om [31]) o he ne magne iza ion o he alloy is addi i e, while in he case o Y2Fe17, Y ium a oms do no ca y any magne ic momen , and he ne magne iza ion o he alloys comes exclusi ely om he Fe subla ice. Assuming ha : (i) he Fe a oms possess he same alues o he magne ic momen in P 2Fe17, YP Fe17 and Y2Fe17 alloys; (ii) he M(T) cu es show a e y simila end o he h ee alloys; and (iii) he P +3 ions in YP Fe17 ha e hei magne ic momen s pa allel o hose o Fe a oms, we could expec ha he subs i u ion o hal o he P +3 ions by Y ones should gi e ise o a dec ease in he magne ic en opy change, espec o ha o P 2Fe17, down o an app oxima e alue gi en by: !SMYP Fe17 "1 2!SMP 2Fe17 +!SMY2Fe17 ( ) . 5 0 0.5 1 1.5 2 2.5 200 250 300 350 400 P 2Fe17 YP Fe17 Y2Fe17 Nd2Fe17 |!SM| (J kg-1 K-1) Tempe a u e, T (K) µ0 !H = 1.5 T 0 0.2 0.4 0.6 0.8 1 0.8 1 1.2 !SM/!SM Peak T/TC Fig. 3. Tempe a u e dependence o he magne ic en opy change in he pseudo-bina y YP Fe17 compound a ound he |∆SM| peak o an applied magne ic ield change µ 0∆H = 1.5 T. Da a o bina y R2Fe17 (R = Y, P and Nd) a e also shown o compa ison. The lines connec ing he calcula ed poin s a e guides o he eyes. Inse : No malized ΔSM/ΔSM Peak s. T/TC o he ou in e me allic alloys. We summa ize in able 2 he alues o TC, |∆SM| (peak alue o µ 0∆H = 1.5 T) oge he wi h he RCP es ima ed by using he h ee c i e ia p e iously de ined. I is wo h no ing ha al hough Y2Fe17 exhibi s he lowes |∆SM| he RCP - 1 is he highes due o a b oade |∆SM|(T) peak as i can be obse ed in he inse o Fig. 3, whe e |∆SM| s. he educed empe a u e T/TC is plo ed. In Fig. 4 he magne ic ield dependence o he RCP o YP Fe17 is depic ed. F om a linea i o he RCP (H) cu es o µ 0H > 1 T, we ha e ex apola ed he alues o an applied magne ic ield change o 2 T in o de o compa e wi h a ailable da e o Gd (see able 2), which is he a che ypical magen o-calo ic ma e ial wi h second o de magne ic phase ansi ions. Figu e 4. Magne ic ield dependence o he Rela i e Cooling Powe (RCP). See ex o de ails. The pseudo-bina y YP Fe17 alloy exhibi s RCP alues compa able o hose o he R2Fe17 compounds wi h R = Y, P o Nd), and bo h RCP -1 and RCP -2 a e ca. 75 % o hose o pu e Gd [32]. Mo eo e , i has been p oposed ha |∆SM|(T) cu es o di e en magne ic ield changes can collapse in o a single mas e cu e, a e an app op ia e no maliza ion, in e omagne ic ma e ials exhibi ing a second o de magne ic phase ansi ion [33]. The mas e cu e is ob ained as ollow [34]: i s ly, he |∆SM|(T) cu es a e no malized o i s maximum alue |∆SM max| o each alue o he applied magne ic ield change. Secondly, he empe a u e axis is escaled 6 using wo di e en e e ence empe a u es: ! " =#T#T C ( ) T 1#T C ( ) T < TC (2) ! " =T#T C ( ) T 2#T C ( ) T > TC (3) whe e T 1 and T 2 a e he empe a u es a which |∆SM| = a × |ΔSM Peak|, wi h 0 ≤ a ≤ 1. In ou case we ha e chosen a = 0.5 ( his alue makes T 1 and T 2 coinciden wi h hose empe a u es a which |∆SM| = |ΔSM Peak|/2 [34]). The mas e cu es o he YP Fe17 compounds a e shown in Fig. 5, and i can be obse ed how he ∆SM/∆SM Peak s. θ cu es o di e en magne ic ield alues almos collapse in o a unique one o each compound. 0 0.2 0.4 0.6 0.8 1 -8 -4 0 4 8 YP Fe17 !SM/!SM Peak ! 0 0.2 0.4 0.6 0.8 1 -3 -2 -1 0 1 2 3 P 2Fe17 YP Fe17 Y2Fe17 Nd2Fe17 "SM/"SM peak ! µ0 !H = 1.5 T Fig. 5. No malized |ΔSM| s. educed empe a u e o he pseudo-bina y YP Fe17 compound. The inse shows he compa ison wi h he cu es o he bina y Y2Fe17, P 2Fe17 and Nd2Fe17 o an applied magne ic ield µ 0H = 1.5 T. Mo eo e , i can be shown ha i he ∆SM/∆SM Peak s. θ cu e o YP Fe17 compound, co esponding o µ0∆H = 1.5 T, is compa ed wi h hose o he bina y R2Fe17 alloys (R = Y, P , Nd, see inse in Fig. 5), he cu es almos o e lap in he ange -1 ≤ θ ≤ 1 ( o empe a u es be ween T 1 and T 2), hus sugges ing ha in hese compounds he empe a u e dependence o he magne ic en opy change exhibi s a simila end [35]. F om a p ac ical poin o iew, he building o such a mas e cu e can be conside ed as an use ul ool o ex apola ing he |∆SM|(H,T) cu es o empe a u e and/o applied magne ic ield alues di e en om hose a ailable in he labo a o y [36]. On he o he hand, i also could help in de ec ing and s udying, om a mo e undamen al iewpoin , di e en co-exis ing magne ic phenomena [37]. Summa y and conclusions The magne ic p ope ies and he magne o-calo ic e ec in he pseudo-bina y YP Fe17 alloy ha e been s udied. Room empe a u e x- ay and neu on powde di ac ion con i m ha he compound c ys allizes in o he o de ed Th2Zn17- ype hombohed al c ys al s uc u e. The magne ic en opy change has been ob ained by he iso he mal magne ic measu emen s, showing ha he in oduc ion o he non-magne ic Y a oms leads o a shi o he empe a u e whe e he maximum o |ΔSM| is ob ained wi h a small educ ion o he peak alue. The calcula ed alues o he RCP in YP Fe17 can each 75 % o he pu e Gd, The e o e, we could expec ha an adequa e mix u e o P o Nd wi h Y in R2Fe17 compounds allows us uning he Cu ie empe a u e a ound oom empe a u e (be ween 285 and 340 K) wi h almos simila alues o he RCP. The e o e, (YP Nd)2Fe17 compounds a e po en ial candida es o i s use in magne ic e ige a ion. Finally, he magne ic en opy change o se e al magne ic ields can be ep esen ed using a mas e cu e ep esen a ion o all hese alloys. 7 Acknowledgmen s We hank Spanish MICINN and FEDER p og amme o inancial suppo h ough he esea ch p ojec MAT2008- 06542-C04-03 and he Slo ak g an agency VEGA 2/0007/09. P.A. is g a e ul o FICyT o Ph.D. con ac . The Slo ak Resea ch and De elopmen Agency (con ac No. VVCE-0058-07), he CLTP as he Cen e o Excellence SAS and P.J. Ša á ik Uni e si y, he CEX Nano luid as he Cen e o Excelence SAS, he 7.FP EU–MICROKELVIN and he SCT’s a he Uni e si y o O iedo (XRD measu emen s) a e also acknowledged. 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C ys allog aphic pa ame e s, cell olume and a omic coo dina es o he s udied R2Fe17 ( mR3 ) compounds ob ained om he bo h NPD and XRD pa e ns in mul i-pa e n i . a (Å) 8.540 (1) c (Å) 12.419 (1) c/a 1.454 V (Å3) 784.3 (2) P /Y (6c) z 0.348 (3) Fe1 (6c) z 0.092 (1) Fe3 (18 ) x 0.293 (1) Fe4 (18h) x z 0.169 (2) 0.489 (1) RB 5.7 χ2 (%) 1.5 Table 2. Cu ie empe a u e, TC, magne ic en opy change, |∆SM| and ela i e cooling powe , RCP, ob ained om he h ee me hods (see ex ). Ex apola ed alues o RCP o a magne ic ield change µ 0∆H = 2 T a e compa ed wi h hose o Gd aken om Re . [32]. Alloy YP Fe17 P 2Fe17 Y2Fe17 Nd2Fe17 Gd TC (K) 290(5) 286(2) 303(4) 339(2) 291(2) |ΔSM| (1.5 T) (J·kg-1·K-1) 2.3 2.6 1.9 2.5 --- T 1 (K) 269 268 278 314 --- T 2 (K) 312 308 334 349 --- RCP-1 (1.5 T) (J kg-1) 98 101 112 85 --- RCP-2 (1.5 T) (J kg-1) 75 78 86 64 --- RCP-3 (1.5 T) (J kg-1) 51 55 56 57 --- RCP-1 (2 T) (J kg-1) 145 156 155 133 200 RCP-2 (2 T) (J kg-1) 111 116 121 98 147 RCP-3 (2 T) (J kg-1) 77 81 82 81 135