Crystal distortion and weak ferromagnetism of Mn3+δGa1−xGex alloys

The compound Mn3Ga (70–74 at.% Mn) has the hexagonal DO19-type structure, and a triangular antiferromagnetic spin structure with a weak ferromagnetic component below the Néel temperature of about 470 K. Below 170 K the hexagonal structure is distorted to an orthorhombic one, accompanied by a steep increase in the ferromagnetic component. X-ray-diffraction experiments and magnetization measurements have been made for a pseudobinary system Mn3+δGa1−xGex. It was found that the DO19-type structure is stable at 600 °C in the whole composition range 0≤x≤1.0 with appropriate values of δ. The Néel temperature of the triangular spin structure decreases with increasing x with a gentle slope. The crystal distortion temperature decreases more steeply and vanishes near x=0.6.