Magnetostriction of La0.75Sm0.25Mn2Si2 compound

• The antiferro–ferromagnetic transition is accompanied by both the volume change and an anisotropic lattice distortion.
• The anisotropic magnetostriction is negative in magnetic fields applied along the c-axis and positive, in the basal plane.
• The coupling constants have smaller values when the magnetic field is applied in the basal plane.
• In small magnetic fields, magnetostriction is proportional to the square of magnetization.

The magnetostriction and magnetization are studied for a quasi-single crystalline sample of the La0.75Sm0.25Mn2Si2 compound which has the spontaneous first-order antiferromagnetic to ferromagnetic (AF–F) phase transition at a temperature of 160 K. For the AF state, the field-induced AF–F transition is observed in magnetic fields directed both along the easy c-axis and in the basal plane. The transition is accompanied by both the volume change ΔV/V = 2.8 × 10−3 and an anisotropic lattice distortion. The anisotropic magnetostriction is negative in magnetic fields applied along the c-axis and positive, in the basal plane. In small magnetic fields, both the volume and anisotropic magnetostrictions are proportional to the square of magnetization. In magnetic fields applied along the c-axis, the field-induced canting of the magnetic moments leads to much larger magnetoelastic deformations than in the basal plane. The values of the magnetovolume coupling constants both along the c-axis and in the basal plane are in agreement with those estimated from the thermodynamic relationships. Very small volume and linear strains are observed for the ferromagnetic state at 250 K. The obtained results suggest that the magnetoelastic effects in these compounds are mainly due to the change of mutual orientations of the Mn magnetic moments of adjacent layers.

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