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Magnetization and remanent magnetization curves for noninteracting single-domain particles whose anisotropy is made up of a cubic magnetocrystalline and an uniaxial components were investigated. For a given cubic anisotropy, the saturation remanence, coercivity, remanence coercivity, and coercivity factor values have been obtained for several different uniaxial anisotropy directions. The corresponding ␦M plots have been constructed for initially thermal or ac demagnetized systems, and a great variety of their shapes has been obtained when the uniaxial anisotropy does not dominate. Coercivity factor values rather higher than those for pure uniaxial or cubic anisotropy particles have been obtained as well, even for already dominating uniaxial anisotropy for some uniaxial anisotropy directions. Thus, it has been shown that one may not safely draw conclusions about interactions from deviations from the zero line in the ␦M plots or coercivity factor values for particles with competing anisotropies without specific analysis for any particular case.

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Magnetization and remanent magnetization curves for noninteracting single-domain particles with cubic magnetocrystalline anisotropy have been calculated, taking into account the first two anisotropy constants. The dependencies of the saturation remanence, coercivity, remanence coercivity, and ␦M plots on the anisotropy constants ratio have been discussed. It has been found that the calculated saturation remanence shows maxima in the vicinity of the spin-reorientation transition points for both negative and positive first cubic anisotropy constants. The remanent magnetization for the case when the face diagonals ͗110͘ are the easiest magnetization orientations has been analytically determined as well. It has been shown that when more than one type of easiest directions coexist, the remanence of the system can only be obtained numerically because of the history dependence of the remanent magnetization for some particles' configurations. The predicted remanence behavior for systems representing spin-reorientation has been compared with that of a Tb 0.6 Ho 0.4 Fe 2 powder sample, and an excellent agreement between numerical and experimental data has been found.

A series of Fe-substituted manganites Bi0.5Ca0.5FexMn1−xO3 (0≤x≤0.6) was synthesized by ceramic technology. The crystal lattice parameters change monotonically with increasing Fe substitution for Mn as found from x-ray powder diffraction and neutron diffraction investigations at room temperature. Magnetic properties were studied between 5 and 1300 K in fields up to 16 kOe. All the compounds are antiferromagnetic below a certain temperature, which decreases with increasing Fe substitution, and for x≥0.1 the antiferromagnetism is accompanied by a weak ferromagnetism. The charge/orbital order exists in the pure form for the compounds without or with very low Fe substitution (x = 0 and 0.05). A new magnetic cluster state exists in the paramagnetic region of manganites with Fe substitution x≥0.3, but only in the presence of magnetic field. The conductivity of compounds measured between 100 and 600 K is of semiconducting type, and there is no magnetoresistivity effect in fields up to 7 kOe.