Structure and magnetic properties of EuMn_xGa_(3-x)

摘要

The crystal structure and magnetic properties of EuMn_xGa_(3-x) intermetallics have been investigated using powder x-ray diffraction and magnetic measurement. EuMn_xGa_(3-x) crystallizes in an orthorhombic structure with a space group of Cmcm, and Z=4. The lattice parameters are a =4.294(1)-4.287(1) A, b=18.50(3)-18.57(3) A, and c=4.384(6)-4.372(9) A. In each unit cell, there are four nonequivalent Ac crystal positions for 4Eu, 4Ga~Ⅰ, 4(Ga~Ⅱ,Mn), and 4Ga~Ⅲ. EuMn_xGa_(3-x) (x< 0.27) intermetallic compounds are antiferromagnetic at low temperature. A magnetic transition from the paramagnetic to the ferromagnetic occurs in EuMn_(0.3)Ga_(2.7) at room temperature when applying a low field of 40 Oe. Moreover, this ferromagnetic order is very weak and sensitive to the applied field. With increasing the applied field, the ferromagnetic order tends to vanish. This phenomenon might be interpreted as the Mn spin state change induced by charge balance at low field.