language: en

[Confidential: not for distribution. Submitted to IOP Publishing for peer review]

21 October 2009

On the electronic origin of the inverse magnetocaloric effect in Ni-Co-Mn-In Heusler alloys

A.N. Vasiliev 1 , O. Heczko 2,3,♣ , O.S. Volkova 1 , T.N. Vasilchikova 1 , T.N. Voloshok 1 , K.V. Klimov 1 , W. Ito 4 , R. Kainuma 4 , K. Ishida 5 , K. Oikawa 5 , and S. Fähler 2
1 Low Temperature Physics and Superconductivity Department, Moscow State University,
Moscow, 119991, Russia
2 IFW Dresden, Institute for Metallic Materials,
P.O. Box 27 01 16, 01171 Dresden, Germany
3 Institute of Physics, Academy of Sciences of Czech Republic,
Na Slovance 2, Prague, Czech Republic
4 IMRAM, Tohoku University,
6-6-02 Aoba-yama, Sendai 980-8579, Japan
5 Department of Materials Science, Graduate School of Engineering,
Tohoku University, 6-6-02 Aoba-yama, Sendai 980-8579, Japan

[♣ corresponding author]

In order to understand the electronic origin of the inverse magnetocaloric effect observed in the Ni-Co-Mn-In system we used the combination of indirect experimental probes as magnetization, resistivity and specific heat. Findings are compared with the band structure of isostructural Heusler alloys like Ni-Mn-Ga. We suggest that the inverse magnetocaloric effect in Ni-Co-Mn-In originates from the high density of states close to Fermi energy. Within the austenite state this causes ferromagnetic band splitting. The structural change to the martensite allows an alternative way to reduce the high density of states at lower temperature, which does not require the band splitting and thus it does not support ferromagnetic order.

PACS: 71.20.Eh, 75.30.Sg, 75.30.Kz