SUSCEPTIBILITY AND EU-151 MOSSBAUER MEASUREMENTS ON THE COMPOUNDS EU(2)PX (X=CL,BR,I) AND ON EU3P2 WITH MIXED-VALENCE AND VALENCE FLUCTUATIONS

The compounds Eu(2)PX (X = Cl,Br,I) have been investigated by (151)EU Mossbauer spectroscopy and magnetic susceptibility measurements. The europium atoms are divalent and their moments order antiferromagnetically at low temperatures. The isomer shifts and the saturation values of the hyperfine fields detected in the Mossbauer spectra are mainly due to the partial occupation of Eu 6s orbitals. Eu2PCl, which has the NaCl type structure, shows unusual spectra. They can be rationalized by a range of electric field gradients, which results from the disordered occupancy of the P3- and Cl- ions within the anion sublattice. (151)EU Mossbauer spectra of Eu3P2 reveal that the compound contains both Eu2+ and Eu3+ ions. Above 150 K thermally activated electron hopping between these ions is observed.