M?ssbauer Effects and Magnetic Properties of Mixed Valent Europium Sulfide, EuPd3S4

EuPd3S4 with a NaPt3O4-type structure was investigated by X-ray diffraction, 151Eu M?ssbauer spectroscopy, magnetic susceptibility, and specific heat measurements. In this compound, Eu2+ and Eu3+ ions exist in the ratio of ca. 1:1. The Debye temperatures of Eu2+ and Eu3+ were determined to be 195 and 220 K, respectively. The isomer shift of Eu2+ in this EuPd3S4 at 300 K is largest among Eu2+ sulfides because of the compression effect of the Eu2+ sites. The temperature dependence of the isomer shifts suggests that a hopping of the electron between Eu2+ and Eu3+ occurs in EuPd3S4. The Eu2+ ion was found to be in the antiferromagnetic state below 3 K from both the magnetic susceptibility and specific heat measurements.