CRYSTAL DISTORTION AND WEAK FERROMAGNETISM OF MN3-GA1-XGEX ALLOYS(DELTA)

The compound Mn3Ga (70-74 at.% Mn) has the hexagonal DO19-type structu re, and a triangular antiferromagnetic spin structure with a weak ferr omagnetic component below the Neel temperature of about 470 K. Below 1 70 K the hexagonal structure is distorted to an orthorhombic one, acco mpanied by a steep increase in the ferromagnetic component. X-ray-diff raction experiments and magnetization measurements have been made for a pseudobinary system Mn3+deltaGa1-xGex. It was. found that the DO19-t ype structure is stable at 600-degrees-C in the whole composition rang e 0 less-than-or-equal-to x less-than-or-equal-to 1.0 with appropriate values of delta. The Neel temperature of the triangular spin structur e decreases with increasing x with a gentle slope. The crystal distort ion temperature decreases more steeply and vanishes near x=0.6.