Magneto-Polaron Formation and Field-Induced Effects with Dilute Doping in LaCo1−y Ni y O3
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Dilute magnetic ion doping in LaCo1−y Ni y O3 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.
KeywordsMagnetic excitations Local distortions Polaron melting
The authors would like to acknowledge valuable discussions with C. Leighton and D. Khomskii. They also express their gratitude to K. Yamada for providing them with the opportunity to grow some of the single crystals at the Institute of Materials Research of Tohoku University. This work is supported by the US Department of Energy under contracts DE-FG02-01ER45927 at the University of Virginia. This work additionally utilized facilities supported in part by the National Science Foundation under Agreement No. DMR-0944772.
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