Magnetic states in Fe65(Ni1 − xMnx)35 alloys

The ferromagnetic-antiferromagnetic concentration transition in Fe65(Ni1 − x Mn x )35 alloys is studied by neutron diffraction and small-angle magnetic neutron scattering (SMNS). The Curie and Neel temperatures are measured, and the antiferromagnetic moments and the cross sections of SMNS by magnetic heterogeneities are determined. The parameters of spin density fluctuations in the heterogeneities are obtained. A cluster mechanism of the nucleation of magnetic phases is revealed, and the spin-glass freezing temperatures are estimated. A low-temperature diagram is constructed for the magnetic states of the alloys.