Relation of magnetic and structural factors in the course of phase transitions in MnAs-Based alloys

A phenomenological analysis of the magnetic and structural phase states obs erved in the manganese arsenide-based alloys over a wide range of temperatu res and pressures has been performed. The unique first-order phase transiti ons from the paramagnetic and metamagnetic states to the ferromagnetic stat e are studied experimentally. It is found that these transitions exhibit ch aracteristic features associated with the magnetostriction suppression of n ucleation when the lability boundary of the paramagnetic phase is absent an d the transition from the metamagnetic state is not thermodynamically "forb idden." The phase behavior of manganese arsenide-based alloys is interprete d within the proposed model. This model accounts for the interrelation of t he magnetic, structural, and elastic properties of alloys and also the spec ific features of phase transformations in real crystals. (C) 2000 MAIK "Nau ka/Interperiodica".