Phase Transitions in Novel Ferromagnetic Shape Memory Alloys Ni-Mn-Sn

Vladimir V. Khovailo 2V V. Koledov 2Vladimir G. Shavrov 2Makoto Ohtsuka 1Toshiyuki Takagi 1

1. Tohoku University, Sendai, Japan
2. Institute of Radio Engineering and Electronics RAS (IRE RAS), Mokhovaya, 11, Moscow 125009, Russian Federation

Abstract

Recently, it was found that for ferromagnetic Heusler alloys Ni2MnSn, Ni2MnIn, and Ni2MnSb, the deviation from stoichiometry results in appearance of martensitic transformation [1]. For these systems, the martensitic transformation temperature decreases upon substitution of Mn for Sn, In or Sb; especially drastic decrease was observed in the NiMnIn system. The compositional dependence of the Curie temperature Tc of the austenite phase was found to be weak, while Tc of the martensite phase is strongly depended on the alloy composition and drastically decreases with decreasing In, Sn or Sb content in all the systems.
In this work we report on new experimental results obtained on two series of novel ferromagnetic shape memory alloy, Ni50+xMn37-xSn13 and Ni50+yMn39-ySn11. They were characterized by differential scanning calorimetry and low-field magnetization measurements. Our DSC measurements revealed that the martensitic transformation temperature Tm in the alloys studied shows a non-monotonous dependence on the Ni excess. Whereas an increase of Tm is observed in both the system as Ni excess increases from 1 at.% to 2 at.%, further substitution of Mn for Ni does not affect martensitic transformation temperature Tm. The low-field magnetic susceptibility measurements were used for determination of Curie temperature TC of these alloys. The results obtained point to a complex magnetic properties of these materials. For instance, some of the alloys exhibit several anomalies on temperature dependence of susceptibility which gives ground to conclude that, contrary to NiMnGa alloys, in the studied Ni-Mn-Sn compositions Curie temperature of martensite is lower than Curie temperature of austenite.

This work was partially supported by Russian Foundation for Basic Research Grants No. 03-02-17443, 04-02-81058, and 03-02-39006.

[1] Y. Sutou et al., Appl. Phys. Lett. 85 (2004) 4358.

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Presentation: oral at E-MRS Fall Meeting 2005, Symposium C, by Vladimir V. Khovailo
See On-line Journal of E-MRS Fall Meeting 2005

Submitted: 2005-05-20 14:05
Revised:   2009-06-07 00:44
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