EPJ Special Topics

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Eur. Phys. J. Special Topics 158, 143-148 (2008)
DOI: 10.1140/epjst/e2008-00667-1

Effects of Fe and Co addition on the magnetoresistance in Ni-Mn-Ga films

K. Koike¹, M. Ohtsuka², M. Matsumoto³, Y. Adachi¹, T. Takagi³ and H. Kato^{1, 4}

¹ Graduate School of Science and Engineering, Yamagata University, 4-3-16 Jonan, Yonezawa, Yamagata 992-8510, Japan
² Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577, Japan
³ Institute of Fluid Science, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577, Japan
⁴ New Industry Creation Hatchery Center, Tohoku University, Aoba-yama 6-6-10, Aoba-ku, Sendai, Miyagi 980-8579, Japan

kkoike@yz.yamagata-u.ac.jp

(Published online: 1 May 2008)

Abstract
Effects of Fe and Co addition on the magnetoresistance MR were investigated in sputtered Ni-Mn-Ga-M (M = Fe, Co) films. With increasing M content, magnetization $\sigma$ enhanced for M = Fe, while it reduced for M = Co. At 300 K, absolute MR value at 1.5 T |MR|_1.5 was about 1%. The value of |MR|_1.5 was found to be decreased with increasing M = Fe content. In the case of M = Co, |MR|_1.5 increased with M content. |MR|_1.5 of the film containing Co 1.6 at.% showed a maximum value of 2.5% at 355 K in the vicinity of the Curie temperature $T_{\rm C}$ . An origin of MR behavior in the present films was suggested to be explained by a s-d scattering model.