Ferromagnetism-to-Spin Glass Phase Transition and Strong Magnetic Field Effect in Ni–Mn Alloys

The electronic structure in the ground state and the response to the magnetic field of Ni–Mn alloys are investigated with use of the Hartree-Fock-Coherent Potential Approximation (HF-CPA) approach. The calculation which distinguishes Mn atoms having antiparallel moments to the bulk magnetization from those with parallel moments shows the occurrence of the second order phase transition at the critical Mn concentration from the ferromagnetic state to the spin glass state in the absence of the magnetic field. The calculated spin susceptibility and bulk magnetization as functions of the magnetic field and the Mn concentration well reproduce the recent experimental results.