Low temperature Schottky anomalies in the specific heat of LaCoO3: Defect-stabilized finite spin states

Measurement of the low temperature specific heat of LaCoO3 single crystals reveals a previously unobserved Schottky anomaly with an energy level splitting, 0.5 meV, that is associated with the first excited spin state of the Co3+ ion. These states persist well below 2 K and have a g-factor around 3.5, consistent with the high-spin spin-orbit triplet, implying the existence of a low density (approximately 0.1% of the sites) of finite-spin Co ions even in the T=0 limit. We propose that these states are trapped at defects and are consistent with the magnetic excitons observed in earlier work.