Document Type

Conference Proceeding

Conference

53rd Annual Conference on Magnetism and Magnetic Materials

Publication Date

2-13-2009

City

Austin, TX

Abstract

Magnetic and structural transitions in the Ni50Mn50−xSnx (x = 10–25) ferromagnetic shape memory alloys are currently of interest. As in Ni–Mn–Ga, these alloys feature high-temperature austenite and low-temperature martensite phases, where the magnetic state is strongly composition dependent. To study the role of chemical ordering in fine-tuning their magnetostructural properties, they were first annealed for 4 weeks/1223 K to achieve structural and compositional homogeneity, and were then further annealed for 1 week ( ∼ 150 K below the reported B2 to L21 transition) at 773 K to increase the degree of chemical ordering. For x = 11, this anneal resulted in a dramatic change in the magnetic ordering temperature. Following the 1223 K anneal, the sample exhibited ferromagnetic ordering at 140 K. After the 773 K anneal, the ferromagnetic transition is at 350 K, a characteristic of the ferromagnetic austenite phase with 15<x<25. Consistent with the magnetization data, transmission electron microscopy examination confirms that the alloy decomposed into two phases with x = 20 and 1. From this result one can conclude that the martensitic transformation occurs only in those compositions where the single phase L21 has been retained in a metastable state on cooling.

Comments

Copyright 2009 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.

The following article appeared in Journal of Applied Physics 105 (2009): 07A921 and may be found at http://dx.doi.org/10.1063/1.3067855.

Copyright Owner

American Institute of Physics

Language

en

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