MAGNETIC AND SPECTRAL STUDIES OF ER2BANIO5 AND OTHER RARE-EARTH NICKELATES

Optical absorption spectra, magnetic susceptibility and magnetization of nickelates R2BaNiO5 (R = Nd-Gd, Dy-Tm) containing isolated Ni-O-Ni chains have been measured. Magnetic ordering temperatures were found to be considerably higher than the temperatures of the maxima in the magnetic susceptibility. Most of the compounds R2BaNiO5 exhibit two metamagnetic transitions. By comparison with neutron diffraction data for Er2BaCuO5 it was shown that the interaction R-Ni dominates and that the magnetic behavior of the rare earth subsystem can be satisfactorily described in a molecular-field framework.