Magnetic order or charge-density wave in La2NiO4 by Mössbauer spectroscopy

Abstract

Measurements of Mössbauer absorption spectra of 57 Fe : La 2 Ni O 4 at 297, 77, and 4.2 K provide evidence, at the lowest temperatures, of magnetic order in a sample containing 57 Fe 3 + -ion impurities and some La 2 + n Ni 1 + n O 4 + 3 n intergrowth. Mössbauer emission spectra of 57 Co : La 2 Ni O 4 at 77 and 4.2 K show magnetic order coexisting with paramagnetism in a sample containing a small concentration of 57 Co -ion impurities and some La 2 + n Ni 1 + n O 4 + 3 n intergrowth. These results are interpreted as evidence for competition between magnetic ordering and charge-density-wave formation among electrons of a narrow σ ∗ x 2 − y 2 band; intergrowths, impurities, and nonstoichiometry favor magnetic ordering.