Synthesis and magnetism of MoCo2O4 spinel thin films

Highlights: • Spinel MoCo₂O₄ films were prepared using pulsed laser deposition. • X-ray photoemission spectroscopy revealed the Mo⁴⁺ and Co²⁺ states in MoCo₂O₄. • The MoCo₂O₄ film showed ferrimagnetism. • There is antiferromagnetic interaction between tetrahedral and octahedral Co ions. Spinel MoCo₂O₄ was synthesized through epitaxial stabilization. X-ray photoemission spectroscopy revealed that the Mo and Co ions mainly exist as Mo⁴⁺ and high-spin (HS) Co²⁺ in the MoCo₂O₄ film, respectively. These valence states were consistent with the prediction based on the relation between lattice constants and ionic radii of cations in various spinel cobaltites. The magnetization of the film was composed of paramagnetic and ferrimagnetic components. Density function theory based calculations suggested that the paramagnetic component mainly corresponds to HS Mo⁴⁺ 4d² ions at the octahedral site, while the ferrimagnetic component is derived from the antiferromagnetic interaction between HS Co²⁺ 3d⁷ ions at the tetrahedral and octahedral sites in inverse spinel Co[CoMo]O₄.