Antiferromagnetism and Metamagnetism in ErFeCuGe4O12

Abstract Polycrystalline ErFeCuGe 4 O 12 has been prepared in a solid-state reaction. It adopts a tetragonal crystal structure; space group P 4/ nbm with a = 9.6416(1), c = 4.7532(1) at room temperature. The Er 3+ cations are in square-antiprismatic coordination and the Fe 3+ and Cu 2+ cations are disordered over one six-coordinate site. The magnetic moments of the three cations adopt an antiferromagnetic arrangement on cooling below 20 K in H = 0 kOe. The magnetic structure consists of ferromagnetic (001) sheets with the spin direction in neighbouring sheets alternating between [001] and [00 1 ] At 5 K the ordered moment of Er 3+ was determined by neutron diffraction to be 7.90(3) µ B and the mean moment of Fe 3+ and Cu 2+ was 2.43(2) µ B . The magnetic structure is unchanged in an applied field of 10 kOe but in fields ≥ 20 kOe the compound begins a metamagnetic transition to a ferromagnetic structure with all atomic moments aligned along [001].