Small angle neutron scattering from disordered [formula omitted]-Mn alloys

Abstract

Neutron small angle scattering measurements on disordered Ni Mn alloys containing 21.8, 23.8,24.8 and 26.3 at% Mn are reported. There is a marked increase in the small angle neutron scattering intensity with decreasing temperature for all the alloys. For the 21.8 at% Mn alloy there is a re-entrant phase which occurs at approximately 100 K but the lineshape of the scattering shows departures away from a Lorentzian at small wavevectors, as has been previously reported in the literature. For the alloys around the critical composition of 25 at% Mn there is an uninterrupted rise in the small angle scattering with temperature. The lineshape of the 23.8 at% Mn alloy also shows some signs of a departure from a Lorentzian. For the remaining alloys the temperature dependence of the inverse correlation length shows the steady evolution of long wavelength magnetic correlations down to 5 K. This is also reflected in the temperature dependence of the extrapolated small angle intensity to Q = 0 which gives a measure of the bulk static susceptibility and is in some agreement with previously reported magnetization and neutron scattering measurements.