Low working temperature near liquid helium boiling point of RNiAl2 (R = Tm, Tb and Gd) compounds with large magnetocaloric effect

A polycrystalline TmNiAl2 compound with transition temperature near the liquid helium boiling point was successfully synthesized. Magnetic measurements show that FM (ferromagnetic) to FM and FM to PM (paramagnetic) transitions take place at 2.4 K and 4.0 K, respectively. Magnetic entropy change (–ΔS...

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Bibliographic Details
Published in:	Journal of applied physics 2019-06, Vol.125 (22)
Main Authors:	Xu, J. W., Zheng, X. Q., Yang, S. X., Shao, S. H., Liu, J. Q., Zhang, J. Y., Wang, S. G., Xu, Z. Y., Wang, L. C., Zhang, S., Zhang, Z. Q., Shen, B. G.
Format:	Article
Language:	eng
Subjects:	Antiferromagnetism Applied physics Boiling points Competitive materials Ferrimagnetism Ferromagnetism Gadolinium Helium Liquid helium Magnetic measurement Mathematical analysis Polycrystals Spin exchange Transition temperature
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Summary:	A polycrystalline TmNiAl2 compound with transition temperature near the liquid helium boiling point was successfully synthesized. Magnetic measurements show that FM (ferromagnetic) to FM and FM to PM (paramagnetic) transitions take place at 2.4 K and 4.0 K, respectively. Magnetic entropy change (–ΔSM) is calculated, and its maximal value [(–ΔSM)max] reaches as high as 20.7 J/kg K with the field change of 0–5 T. The low transition temperature together with large (–ΔSM)max at the liquid helium temperature zone originates from the weak spin-spin exchange interaction between Tm atoms. For a clear comparison, the magnetocaloric effect (MCE) of polycrystalline RNiAl2 (R = Tb and Gd) samples was also prepared and investigated. For the TbNiAl2 compound, FIM (ferrimagnetic) to AFM (antiferromagnetic) and AFM to PM transitions occur at 11.0 K and 21.5 K, respectively. As for the GdNiAl2 compound, an FM to PM transition occurs at 30.5 K. The value of (–ΔSM)max under the field change of 0–5 T is calculated to be 11.8 J/kg K and 17.3 J/kg K for TbNiAl2 and GdNiAl2, respectively. Compared with other RNiAl2-series MCE materials, TmNiAl2 exhibits the lowest working temperature and relatively larger (–ΔSM)max. The large MCE at low temperature indicates that TmNiAl2 is competitive among the MCE materials working at a liquid helium temperature zone.
ISSN:	0021-8979 1089-7550