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),k, 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)muB and 2.1(3)muB 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.