The antiferromagnetic structure of ErPtGe2

Neutron powder diffraction and susceptibility measurements were performed on ErPtGe2. It crystallizes in the orthorhombic YIrGe2-type structure (space group Immm, Z=8) and the rare-earth atoms are located on two different sites (4h, 4i). Structural parameters have been refined; the room-temperature lattice parameters are a=4.282(6) A, b=16.240(3) A and c=8.669(2) A. At 2.9 K, ErPtGe2 undergoes a magnetic phase transition into a canted antiferromagnetic structure of the Er moments. The propagation vector is k=0,12,12. The magnetic moment values at 1.8 K are 8.3(2)μB and 2.1(3)μB on the 4i and 4h sites, respectively, with the main components along the b- and a-axis, respectively, showing inclination angles of about 20°each.