Magnetism and 151Eu Mossbauer spectra of α- and β-Eu2GeS4

Single phase alpha-EU2GeS4 was prepared by oxidation of Eu2Ge with sulfur. Magnetic susceptibility measurements reveal Curie behavior with an experimental magnetic moment of 7.85(5) mu(B)/Eu, compatible with divalent europium. Eu2GeS4 orders antiferromagnetically at T-N = 5.0(5) K and undergoes a metamagnetic transition at a low critical field of about 0.3(2) T. The saturation magnetization at 2 K and 5.5 T is 6.70(2) mu(B)/Eu. Despite the two crystallographically different europium sites, Eu-151 Mossbauer spectroscopy experiments show a single signal at 78 K with an isomer shift delta = - 12.44(8) mm/s and a line width Gamma = 2.5(l) mm/s indicating purely divalent europium. At 4.2 K weak magnetic hyperfine field splitting is observed. No anomaly was detected in the susceptibility data and the Eu-151 Mossbauer spectra when heating the ferroelectric sample above the Curie temperature of 335 K.