Magnetization and Magnetostriction of LaFe 11.2 – х Mn x Co 0.7 Si 1.1 Alloys ( x = 0.1, 0.2, 0.3) in Pulsed Magnetic Fields

The magnetization and magnetostriction of polycrystalline LaFe 11.2 – х Mn x Co 0.7 Si 1.1 alloys ( x = 0.1, 0.2, 0.3) were measured in pulsed magnetic fields up to 180 kOe in the temperature region of 80–270 K. The substitution of Fe atoms by Mn atoms shifts Т С towards lower temperatures and has no effect on the saturation magnetization. The observed magnetization–field dependence M ( H ) near Т С is typical of the second-order phase transitions, whereas the magnetization–temperature dependence M ( Т ) above Т С in strong magnetic fields indicates the occurrence of a first-order phase transition. The magnetovolume effect ∆ V / V attains 0.81% in a field of 180 kOe. Magnetostriction asymmetry with respect to the maximum temperature of the effect in strong magnetic fields and magnetic-field hysteresis of magnetostriction have the first-order phase transition features.