RESUMEN
The spin reorientation temperature T(SR) of stoichiometric Fe(3)O(4), as well as of magnetite with a small number of vacancies and magnetite containing a low concentration of Ti, Zn, Al and Ga was measured on single-crystal samples using the ac susceptibility. In the same experiment the temperature T(V) of the Verwey transition was also found. The results show that a correlation between T(SR) and T(V) exists. The electronic structure of the compounds studied was determined using the density-functional-based GGA + U method. For stoichiometric magnetite the first and second cubic anisotropy constants were calculated, while for magnetite with defects the distribution of electron density using the 'atoms in molecules' approach was determined. Based on a combination of experimental results with the electronic structure calculations an explanation of the temperature dependence of the magnetocrystalline anisotropy of magnetite is suggested.
Asunto(s)
Óxido Ferrosoférrico/química , Algoritmos , Anisotropía , Química Física/métodos , Cristalización , Electrónica , Electrones , Iones , Modelos Moleculares , TemperaturaRESUMEN
Approach for interpretation of nuclear magnetic resonance (NMR) spectra in magnetic materials is presented, consisting in employing the anisotropy of hyperfine interaction. The anisotropic parts of hyperfine magnetic fields on (57)Fe nuclei are calculated ab initio for a model example of lithium ferrite and utilized to assign the experimental NMR spectral lines to iron sites in the crystal structure.