Magneto-Polaron Formation and Field-Induced Effects with Dilute Doping in LaCo1−y Ni y O3

Abstract

Dilute magnetic ion doping in LaCo1−yNiyO3 with y≤1 % leads to the formation of isotropic magnetic clusters that exhibit intracluster interactions which are ferromagnetic in nature. The clusters are comprised of Ni ions surrounded by six magnetically polarized Co ions. The Ni spin is delocalized from the Ni3+ ion but is confined in the vicinity of the six Co coordinated environment forming small magneto-polarons. The cluster ground state is estimated from bulk magnetization to be about gS∼10, in contrast to LaCoO3, which is not magnetic. Using neutron spectroscopy, transitions are observed between the lowest energy levels indicating that the cluster ground state is split. Under a magnetic field of 1 Tesla, the transitions are suppressed while with increasing temperature, the intracluster transitions are overshadowed by the activation of the Co3+ ions to the intermediate spin state.