We report the observation of contrasting magnetic behavior in cobalt ferrite ͑CFO͒ thin films deposited on single crystalline magnesium oxide ͑MgO͒ and strontium titanate ͑STO͒. Epitaxial films on MgO ͑100͒ with a lattice mismatch of 0.35% showed out-of-plane anisotropy whereas the films on STO ͑100͒ with a lattice mismatch of 7.4% displayed in-plane anisotropy. Stress anisotropy calculated from angle-dependent x-ray diffraction analysis confirmed that the change in anisotropy originates from the lattice mismatch. An additional low-field switching characteristic is observed in the M-H loops of the CFO films, which became prominent with lowering temperature as also evidenced from the rf transverse susceptibility measurements. The obtained results revealed that the low field switching is associated with the film-substrate interface.
In this paper, we demonstrate through experiments and analysis that the most probable mechanism for the observed ferromagnetism in 2% Mn-doped ZnO thin films is a combination of intrinsic and carrier-mediated interaction of the magnetic moments. While no impurity-phase contributions were detected, a strong correlation between effective carrier densities and ferromagnetism was established. Magnetism in amorphous films with high defect densities were described by a bound magnetic polaron model whereas that in highly conducting films was consistent with a Ruderman-Kittel-Kasuya-Yosida exchange mechanism.
Perovskite oxides show an amazing diversity of electronic and magnetic properties along with a myriad of structural variants and phase transitions. Large thermal changes may be driven near the ferroic phase transitions in perovskite oxides using magnetic, electric, and stress fields to manipulate conjugate order parameters. The ensuing magnetocaloric, electrocaloric, and mechanocaloric effects can be utilized for environment‐friendly and high‐efficiency solid‐state cooling applications. In this review the details of these caloric effects in perovskite oxides both from a chronological perspective and from the viewpoint of the recent advances in multiple caloric phenomena are described. The authors highlight the role of interfaces in oxide thin films for the different caloric effects and address some of the outstanding challenges for the fundamental understanding and practical implementation of perovskite oxides in solid state refrigeration.
Highly packed LN-type ZnSnO3 NW arrays are grown on ZnO:Al/Si substrates using a hybrid pulsed laser deposition and solvothermal process. Unique "welding" mechanism structurally joins adjacent ZnSnO3 NWs to form a nearly impervious 20 μm thick nanostructured film that shows high P r of 30 μC/cm(2) at a low E c of 25 kV/cm for the first time.
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