MA Co_xCu_<100-x>合金の磁気抵抗及び磁性の温度依存性  [in Japanese] Temperature Dependence of the Magnetoresistance and Magnetism for MA Co_xCu_<100-x> Alloys  [in Japanese]

Co_xCu_<100-x> binary alloys with Co concentrations of x=5-30 were produced by mechanical alloying. We examined the magnetoresistance (MR) and magnetism in the temperature range from 5 K to 300 K for the as-milled Co_xCu_<100-x> alloys, and investigated the relationship between the MR and the magnetization. The MR for the as-miled samples is characterized as follows: (1) For samples with x≦15, the MR ratio increases at low temperature (5.5% at 5 K), and changes in proportion to the square of the magnetization, M^2, (2) for a sample with x = 20, the MR ratio measured at temperatures below 120 K shows a constant value (〜3%), and is not proportional to M^2 in this temperature range, and (3) for samples with x≧25, the MR ratio decreases with decreasing temperature, and is not proportional to M^2. The magnetization measured at high temperature shows superparamagnetic behavior for samples with x≦20, and has a ferromagnetic component for samples with x ≧ 25.