The Ground State of fcc Nickel-Base Ferromagnetic Disordered Alloys

Abstract

Possible causes of the instability of the strong ferromagnetism in fcc nickel-base disordered alloys are discussed. In the case of Ni-Mn alloys it is caused by the appearance of Mn atoms with magnetic moments antiparallel to the bulk magnetization. Although the same situation is expected in the case of Ni-Fe alloys in the Hartree-Fock approximation, the many-body effect arising from the electron-magnon scattering is more likely to be responsible for the instability of the strong ferromagnetic state in this alloy system. The reasoning leading to this conclusion is discussed in detail. The spin fluctuation in the ground state in Ni-Fe alloys after the onset of the instability is expected then to become large.