Magnetic anisotropy in Ni-Mn-Ga martensites

被引:142
作者
Straka, L [1 ]
Heczko, O [1 ]
机构
[1] Helsinki Univ Technol, Dept Engn Phys & Math, Biomed Engn Lab, Espoo 02015, Finland
关键词
D O I
10.1063/1.1555982
中图分类号
O59 [应用物理学];
学科分类号
摘要
We study the temperature dependence of the magnetic anisotropy of three different martensites known to exist in the Ni-Mn-Ga alloys. The anisotropy constants were determined from magnetization curves measured at different temperatures. The anisotropy of five-layered modulated tetragonal martensite is uniaxial with easy magnetization direction along short crystallographic axis. At room temperature K-1(rt)=1.65x10(5) J m(-3) and K-2 is negligible. Seven-layered modulated orthorhombic martensite exhibits easy magnetization direction along the shortest crystallographic axis. K-1(rt)=1.7x10(5) J m(-3) and K-2(rt)=0.9x10(5) J m(-3) referring to hard and mid-hard magnetization axes. Nonmodulated tetragonal martensite possesses a uniaxial anisotropy with easy plane and hard magnetization direction along the long crystallographic axis with K-1(rt)=-2.3x10(5) J m(-3) and K-2(rt)=0.55x10(5) J m(-3). The temperature dependence of K-1(T) of five-layered martensite follows magnetization power law with exponent n=3 suggesting a single ion origin of the magnetic anisotropy in Ni-Mn-Ga martensite. (C) 2003 American Institute of Physics.
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页码:8636 / 8638
页数:3
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