013906-5 Ingale et al. J.Appl.Phys.102.013906(2007 ACKNOWLEDGMENT The authors thank the Defence Research Development Organization(DRDO), India, for the financial support to carry out this work V. K. Pecharsky and K. A. Gschneidner, Jr, Phys. Rev.Lett.78,4494 V. K Pecharsky and K. A. Gschneidner, Jr, Appl. Phys. Lett. 70, 3299 3S. J. Murray, M. A Marioni, A M. Kukla, J. Robinson, R C O'Handley and S M. Allen, J. Appl. Phys. 87, 5774(2000) F-X.Hu. B.-G. Shen, J.R. Sun, Z.H Cheng, and X.X. Zhang, J Phys. Condens Matter 12, L691(2000) O. Tegus, E. Bruck, K. H.J. Buschow, and F R. de boer, Nature 415, 150 (2002) L. Pareti, M. Solzi, F. Albertini, and A. Paoluzi, Eur. Phys. J. B 32, 303 (2003) E. Bruck, O. Tegus, X. W. Li, F. R. de Boer, and K. H. J. Buschow, FIG.6. Magnetic entropy changes in the (a) Nis4sMn2o3Ga24g:(b)A. Fujita, S Fujieda, Y. Hasegawa, and K Fukamichi, Phys. Rev. B 67. MnIRgGa26.1: and(c) Niss 2 Mn& Ga26.7 alloys in the magnetic field 104416(2003) ge 1.2 T A. Cherechukin, T. Takagi, M. Matsumoto, and V. D. Buchel'nikov, Phys. the Niss. 2Mn181 Ga26.7 alloy, the ASM value distributes slowly F-X. Hu, B.G. Shen, and J -R. Sun, Appl. Phys. Lett. 76, 3460(2000) over a large span of temperature AT-16 K between the TM IJ. Marcos. A Planes. L. Manosa. F. Casanova. X. Battle. A. Labarta, and B. Martinez, Phys. Rev. B 66. 224413(2002) and Tc values. A coupled magnetostructural transformation, J. Marcos, L Manosa, A Planes, F Casanova, XBattle, and A. Labarata AT-0, and a large MCE appear to be interesting for active Phy.Rev.B68,094401(2003) E Bruck, J. Phys. D 38, R381(2005) magnetic refrigerant applications of Nis4&Mn,o Ga,4g alloy F Albertini, A.Paoluzi, LPareti,M.Solzi, L.Righi,E.Villa,S.Besseg- near room temperature hini,and F. Passaretti, J. Appl. Phys. 100, 023908(2006) L CONCLUSIONS H. Wada and Y. Tanabe, Appl. Phys. Lett. 79, 3302(2001) X. Bohigas, J. Tejada, E. Barco, X. X. Zhang, and M. Sales, Appl. Phys The nonmodulated martensite, the seven-layer Lett73,390(1998) E. Albertini, L. Pareti, A. Paoluzi, L. Morellon, P. A. Algarabel, M.R lated martensitic, and the austenite phases were obser Ibarra, and L. Righi, J. AppL. Phys. 81, 4032(2002) room temperature in Nis48Mn203 Ga249, Niss MnI8s 11. Babita, M. Manivel Raja, R Gopalan, V Chandrasekharan,and SRam, and Niss. 2 Mn,8. Ga26.7 alloys, respectively. Among these al- J. Alloys Compd. 432, 23(2007) loys, Nis4.8Mn203Ga24. displayed an enhanced MCE, with as J. Pons, V.AChernenko, R. Santamarta, and ECesari, Acta Mater.48 large ASM value as.0 J/kg K, at 332 K in an applied field 2U.Gaitzsch,SRoth,B.Rellinghaus, and L.Schultz,J. Magn.Magn. .2 T. The origin of the ASy is related to the coincidence of Mater..305,275(2006) structural and magnetic transition temperatures(TM, Tc V. V Martynov and VV Kokorin, J. Phys. m 2, 739(1992) 351 K). Such an appreciable ASy value in such low fields V.V.Martynov, J Phys. IV 5, 91(1995) will enable the material to operate in fields produced by per-YGe, O Soderberg, N Lanska, A Sozinov, K. Ullakko, and V.K. Lin manent magnets. Thus, the Nis4. Mn20.3Gaz49 alloy seems to , droos, J Phys. IV 2, 921(2003) V. A. Chernenko. E. Cesari. V. V. Kokorin. and L. N. vitenko. Scr. Metall. be one of the promising compositions in the Ni-Mn-Ga sys- Mater. 33, 1239(1995) tem for room-temperature magnetic refrigeration and other 25C. Jiang, Y. Muhammad, L. Deng, w. Wu, and H. Xu, Acta Mater. 52 applications. 2779(20the Ni55.2Mn18.1Ga26.7 alloy, the
SM value distributes slowly over a large span of temperature
T16 K between the TM and TC values. A coupled magnetostructural transformation,
T→0, and a large MCE appear to be interesting for active magnetic refrigerant applications of Ni54.8Mn20.3Ga24.9 alloy near room temperature. IV. CONCLUSIONS The nonmodulated martensite, the seven-layer modu￾lated martensitic, and the austenite phases were observed at room temperature in Ni54.8Mn20.3Ga24.9, Ni55Mn18.9Ga26.1, and Ni55.2Mn18.1Ga26.7 alloys, respectively. Among these al￾loys, Ni54.8Mn20.3Ga24.9 displayed an enhanced MCE, with as large
SM value as −7.0 J/kg K, at 332 K in an applied field 1.2 T. The origin of the
SM is related to the coincidence of structural and magnetic transition temperatures
TM, TC =351 K. Such an appreciable
SM value in such low fields will enable the material to operate in fields produced by per￾manent magnets. Thus, the Ni54.8Mn20.3Ga24.9 alloy seems to be one of the promising compositions in the Ni-Mn-Ga sys￾tem for room-temperature magnetic refrigeration and other applications. ACKNOWLEDGMENT The authors thank the Defence Research & Development Organization
DRDO, India, for the financial support to carry out this work. 1 V. K. Pecharsky and K. A. Gschneidner, Jr., Phys. Rev. Lett. 78, 4494
1997. 2 V. K. Pecharsky and K. A. Gschneidner, Jr., Appl. Phys. Lett. 70, 3299
1997. 3 S. J. Murray, M. A. Marioni, A. M. Kukla, J. Robinson, R. C. O’Handley, and S. M. Allen, J. Appl. Phys. 87, 5774
2000. 4 F.-X. Hu, B.-G. Shen, J.-R. Sun, Z.-H. Cheng, and X.-X. Zhang, J. Phys.: Condens. Matter 12, L691
2000. 5 O. Tegus, E. Brück, K. H. J. Buschow, and F. R. de Boer, Nature 415, 150
2002. 6 L. Pareti, M. Solzi, F. Albertini, and A. Paoluzi, Eur. Phys. J. B 32, 303
2003. 7 E. Brück, O. Tegus, X. W. Li, F. R. de Boer, and K. H. J. Buschow, Physica B
Amsterdam 327, 431
2003. 8 A. Fujita, S. Fujieda, Y. Hasegawa, and K. Fukamichi, Phys. Rev. B 67, 104416
2003. 9 A. Cherechukin, T. Takagi, M. Matsumoto, and V. D. Buchel’nikov, Phys. Lett. A 326, 146
2004. 10F.-X. Hu, B.-G. Shen, and J.-R. Sun, Appl. Phys. Lett. 76, 3460
2000. 11J. Marcos, A. Planes, L. Manosa, F. Casanova, X. Battle, A. Labarta, and B. Martinez, Phys. Rev. B 66, 224413
2002. 12J. Marcos, L. Manosa, A. Planes, F. Casanova, X. Battle, and A. Labarata, Phys. Rev. B 68, 094401
2003. 13E. Brück, J. Phys. D 38, R381
2005. 14F. Albertini, A. Paoluzi, L. Pareti, M. Solzi, L. Righi, E. Villa, S. Besseg￾hini, and F. Passaretti, J. Appl. Phys. 100, 023908
2006. 15H. Wada and Y. Tanabe, Appl. Phys. Lett. 79, 3302
2001. 16X. Bohigas, J. Tejada, E. Barco, X. X. Zhang, and M. Sales, Appl. Phys. Lett. 73, 390
1998. 17F. Albertini, L. Pareti, A. Paoluzi, L. Morellon, P. A. Algarabel, M. R. Ibarra, and L. Righi, J. Appl. Phys. 81, 4032
2002. 18I. Babita, M. Manivel Raja, R. Gopalan, V. Chandrasekharan, and S. Ram, J. Alloys Compd. 432, 23
2007. 19J. Pons, V. A. Chernenko, R. Santamarta, and E. Cesari, Acta Mater. 48, 3027
2000. 20U. Gaitzsch, S. Roth, B. Rellinghaus, and L. Schultz, J. Magn. Magn. Mater. 305, 275
2006. 21V. V. Martynov and V. V. Kokorin, J. Phys. III 2, 739
1992. 22V. V. Martynov, J. Phys. IV 5, 91
1995. 23Y. Ge, O. Söderberg, N. Lanska, A. Sozinov, K. Ullakko, and V. K. Lin￾droos, J. Phys. IV 2, 921
2003. 24V. A. Chernenko, E. Cesari, V. V. Kokorin, and I. N. Vitenko, Scr. Metall. Mater. 33, 1239
1995. 25C. Jiang, Y. Muhammad, L. Deng, W. Wu, and H. Xu, Acta Mater. 52, 2779
2004. FIG. 6. Magnetic entropy changes in the
a Ni54.8Mn20.3Ga24.9;
b Ni55Mn18.9Ga26.1; and
c Ni55.2Mn18.1Ga26.7 alloys in the magnetic field change 1.2 T. 013906-5 Ingale et al. J. Appl. Phys. 102, 013906 2007