Magnetization as a function of field and temperature for a ferromagnetic Heusler alloy ${\mathrm{Ni}}_2\mathrm{MnGa}$ is reported. Magnetization above the Martensitic transition displays a field-dependent peak effect, a direct magnetic evidence of premartensitic phase. At low fields, the peak effect occurs at a temperature consistent with the observations of the micromodulated structure transition seen from neutron scattering, electron microscopy, and ultrasonic studies in this compound. At high fields, the peak effect is suppressed. The strong field dependence of the peak temperature suggests a large magnetoelastic interaction in the intermediate phase.

• Received 2 June 1998

DOI:https://doi.org/10.1103/PhysRevB.58.11127