Institute of Materials Science, University of Tsukuba
○Ejaz Ahmed Yuji Fuji Miwako Takahashi Hiroshi Iwasaki Ken-ichi Ohshima

We have already identified the crystal structure of newly designed CuMPt₆ (M=3d elements) alloys by X-ray, electron and neutron diffraction methods [1, 2]. In the analysis, a double step ordering without any change of cubic symmetry was firstly discovered for CuMnPt₆ alloy. In order to obtain more quantitative information on structure and magnetism of the alloys, we have performed in-situ X-ray diffraction, electrical resistivity and magnetic susceptibility measurements. First, the transition temperatures from disordered to Cu₃Au type ordered phases were determined in a temperature range from 750 ^oC for M=Mn to 1010 ^oC for M=Fe. Secondly, the values of the resistivity were determined as (5~7)x10^-5 ohm-cm except for M = Mn with 6x10^-4 ohm-cm. Thirdly, a general trend in magnetic properties is as follows: paramagnetic - spinglass like - ferromagnetic - paramagnetic with increasing atomic number. The nature of the magnetism is not much affected by the structural phase changes in the present alloys, though a little change is observed in T_c or T_g due the structural phase change. The original nature of the magnetism in the ternary CuMPt₆ alloys remains the same as in the binary MPt₃ one. We believe that the unpaired electrons in 3d-elements are responsible for the magnetic properties of CuMPt₆ alloys.

[1]. M. Takahashi, A. K. Das, R. Nakamura, H. Iwasaki, T. Shishido and K. Ohshima: J. Phys. Soc. Jpn. 75 (2006) 013601-1.
[2]. A. K. Das, R. Nakamura, M. Takahashi, H. Iwasaki, T. Shishido and K. Ohshima: J. Phys. Soc. Jpn. 75 (2006) 024604.