ELECTRON-SPIN-RESONANCE OF LA2-XSRXNIO4+DELTA

We present a room temperature ESR study of H-2-reduced La2-xSrxNiO4+de lta with 0 less-than-or-equal-to x less-than-or-equal-to 0.5 and delta less-than-or-equal-to 0. Samples prepared by a precursor method based on citrate solutions show ESR spectra which can be attributed to para magnetic Ni ions in the neighborhood of 0 vacancies. The evolution of the spectrum with x is in agreement with magnetic and structural varia tions previously determined by neutron diffraction experiments. Sample s prepared by a standard ceramic method showed contamination (approxim ately 1%) with metallic Ni particles, which prevented their ESR study.