Spin glassiness and ferromagnetism in disordered Ni-Mn (invited)

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Abstract
With decreasing Mn concentration near 25 at. %, disordered Ni-Mn alloys are seen to evolve from a characteristic spin-glass behavior, with the magnetic polarizability rapidly increasing, to a magnetic behavior that signifies the onset of ferromagnetic order and the appearance of a spin-glass-like phase at lower temperatures. Moreover, the latter phase is ‘‘mixed’’ in that its equilibrium state (in the fields applied during cooling) manifests a spontaneous ferromagnetic moment, while its magnetization reversals with field exhibit the unidirectional anisotropy of a spin glass. The unusual magnetic properties of the mixed phase in the zero-field-cooled state can be ascribed to a domain structure in which the domains have unidirectional anisotropies of random orientation.