Cold-working effect on magnetic properties in the Heusler alloys

The cold-working effect on the average magnetic interaction (J̄), the spontaneous magnetization at 0 K (M₀), and the magnetic transition temperature (Θₘ) in the Heusler alloys is formulated by means of dislocation theory with consideration of ferromagnetic and antiferromagnetic interactions between Mn atoms. The Mn atoms near the antiphase boundaries produced by plastic deformation have a different atomic environment (i.e., a different J̄ value) from that in the normal state and cause a marked effect of cold working on the magnetic properties. The numerical estimation is given for two ferromagnetic Heusler alloys, Pd₂MnSn and Ni₂MnSn. A remarkable reduction of M₀ in the plastically deformed Pd₂MnSn, which was experimentally observed by previous investigators, is interpreted in the light of the present calculated results.