During a research on multifunctional materials all functional properties that can be triggered with external stimulus are o vital importance. When considering multiferroics the external stimulus is mainly the electric field, which in addition to the changes in magnetization also induces caloric effect. In turn, this effect generate changes in lattice dynamics, therefore, we need to precisely understand it. This was our motivation to develop the theory of electrocaloric effect, which accurately describes and enables a quantitative calculation of the effect.
COBISS.SI-ID: 1002235
A microstructural investigation of epitaxial CoFe2O4 films grown by pulsed laser deposition on single crystal SrTiO3 substrates was performed. We quantitatively analysed the microscopic mechanisms for structural mismatch compensation and the mode of the film growth. Quantitative high-resolution transmission electron microscopy showed that most of the compensation occurs by formation of (4 0 0) edge dislocations in the film. The growth mode changes from layer-by-layer growth to island growth.
COBISS.SI-ID: 1751035
We studied the magnetic properties of epitaxial CoFe2O4 films as a function of oxygen post-annealing and film thickness. All as-deposited films exhibited similar magnetic properties with Ms of approximately 50% of the bulk saturated magnetization (Ms). After the post-annealing the Ms changed as a consequence of crystallographic restructuring of the film. Cation ordering in 100nm thick films reduced Ms, whereas re-oxidation increased Ms for thinner films. 13nm films, annealed for 1h, reached the bulk Ms. For even thinner films the quantum-size effect reduced Ms.
COBISS.SI-ID: 1751035
The electrocaloric effect in a 0.92PbZn1/3Nb2/3O3-0.08PbTiO3 single crystal was measured by a direct calorimetric technique as a function of sample temperature and electric field. The temperature of the maximum electrocaloric effect was found to coincide with the ferroelectric transition temperature. We present a theoretical description based on mean-field theory that gives a satisfactory description of the temperature and electric field dependence of the experimentally observed electrocaloric effect.
COBISS.SI-ID: 1495291
: In functional oxide materials the so called molecular auxetic behavior is extremely rare. We discovered it in CoFe2O4 spinel structure. The CoFe2O4 epitaxial thin film under compressive axial strain reduces its cell dimensions also in the transverse direction with a Poisson’s ratio of -0.85. We identified the hinge-like honeycomb network in the spinel structure that is responsible for the negative Poisson’s ratio. The observed phenomenon importantly affects functional properties of CoFe2O4 and enables a construction of a new class of nano-devices.
COBISS.SI-ID: 1382651