Magnetostriction Constants of Face-Centered Cubic Nickel-Copper and Nickel-Cobalt Alloys

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The magnetostriction constants, λ_<100> and λ_<111> of face-centered cubic Ni-Cu and Ni-Co alloys have been determined at room temperature, using single-crystal disc specimens and the strain gauge technique. In Ni-Cu alloys, both constants are negative irrespective of the composition and their absolute values decrease monotonously with increasing copper content. In Ni-Co alloys, the concentration dependence is quite different for λ_&tl;100> and λ_<111> ; λ_<111> is negative irrespective of the composition, showing a flat minimum centered at about 30% Co, while λ_<100> increases almost linearly with increasing cobalt content, passing through zero at about 20 % Co, and eventually reaches to a large value of 116×10^<-6> at 55 % Co. It has been found that the experimental results on the concentration dependence of the magnetostriction constants of face-centered cubic Ni-Co alloys agree quite well with the Vonsovsky-Neel formula for binary cubic solid solutions consisting of two types of magnetic atoms A and B, which is of the form λ=C(N_A^2E_<AA>+2N_AN_BE_<AB>+N_B^2E_<BB>), where λ is λ_<100> or λ_<111>, C the constant, N_A and N_B the concentrations of the A and B atoms, respectively, and E_<AA>, E_<AB> and E_<BB> the energies of magnetic interaction between A and A atoms, between A and B atoms, and between B and B atoms, respectively. For binary cubic solid solutions consisting of magnetic and non-magnetic atoms such as Ni-Cu alloys, it is shown theoretically and experimentally that the following relations hold approximately among the magnetostriction constants, saturation magnetization, I_s, and concentration of non-magnetic atoms, N : λ_<100>∝ I_s^2∝ (1 -N/N_c)^2, where N_c is the concentration where the spontaneous magnetization disappears.
東北大学の論文

Magnetostriction Constants of Face-Centered Cubic Nickel-Copper and Nickel-Cobalt Alloys

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