It is well known that the spin-chain compound ${\text{Ca}}_3{\text{Co}}_2{\text{O}}_6$ exhibits interesting plateaus in the magnetization as a function of the magnetic field at low temperatures. The origin of them is still controversial. In this paper, we study the thermal behavior of this compound with a single-flip Monte Carlo simulation on a triangular lattice and demonstrate the decisive influence of metastable states on the splitting of the ferrimagnetic $1/3$ plateau below 10 K. We consider the ${\left[{\text{Co}}_2{\text{O}}_6\right]}_n$ chains as giant magnetic moments described by large Ising spins on planar clusters with open boundary conditions. With this simple frozen-moments model we obtain stepped magnetization curves which agree quite well with the experimental results for different sweeping rates. We describe particularly the out-of-equilibrium states that split the low-temperature $1/3$ plateau into three steps. They relax thermally to the $1/3$ plateau, which has long-range order at equilibrium. Such metastable states are further analyzed with snapshots unveiling an interlinked mobile domain walls structure that is responsible for the observed behavior of the $1/3$ plateau. A comparison is also given of our classical Monte Carlo results with exact diagonalization results in small triangular quantum clusters, providing further support for our thermal description of this compound.

Linear asymmetrical magnetoimpedance (MI) has been obtained in thin multilayer strips of exchange-coupled FeNi(5 nm)/IrMn(15 nm)/FeNi(40 nm)/Cu(100 nm)/FeNi(40 nm)/IrMn(15 nm)/FeNi(5 nm), in which the MI response is enhanced by including a Cu layer between the two 40 nm NiFe layers. The antiferromagnetic layer creates an exchange bias that shifts both the hysteresis loop and the MI response. The asymmetrical MI peak positions are shifted to higher magnetic field as the probe frequency increases. Linear MI behavior can be tuned around zero external field without the need for external biasing fields or additional coils, by changing the frequency. The impedance of a planar magnetic conductor was modeled based on a modified Stoner–Wohlfarth energy density.

We present hybrid density functional calculations suggesting that magnetism in cubic SrTi_1−xCo_xO_3−δ (STCO) with x = 0.25 is sensitive to the nearest neighbor arrangement of the Co and the presence of oxygen vacancies. Spin polarized calculations for x = 0.25 in which the nearest neighbor (nn) Co spacing is a, $\sqrt{2}a$ or $\sqrt{3}a$ with a the lattice parameter predict lowest energies for the $\sqrt{2}a$ nn separation and favor the ferromagnetic state. Oxygen deficiency ($\delta =0.125$ ) lowers the average Co valence state and favors mixed valence and spin states (high spin for the Co adjacent to the vacancy and low for the non-adjacent Co), an increase of the band gap and an expansion of the lattice parameter compared to stoichiometric STCO in which both Co ions are low spin. Predicted configurations of the two neighboring Co ions are ($t_{2g}^5{e}_g^0, t_{2g}^5{e}_g^0$ ) and ($t_{2g}^4{e}_g^2, t_{2g}^6{e}_g^0$ ) with average 1.0 and 1.6 ${\mu }_B/Co$ for stoichiometric and 1-O-vacancy systems, respectively.

In this work, we report the magnetocaloric effect (MCE) in two systems of non-interactive particles: the first corresponds to the Landau problem case and the second the case of an electron in a quantum dot subjected to a parabolic confinement potential. In the first scenario, we realize that the effect is totally different from what happens when the degeneracy of a single electron confined in a magnetic field is not taken into account. In particular, when the degeneracy of the system is negligible, the magnetocaloric effect cools the system, while in the other case, when the degeneracy is strong, the system heats up. For the second case, we study the competition between the characteristic frequency of the potential trap and the cyclotron frequency to find the optimal region that maximizes the $\Delta T$ of the magnetocaloric effect, and due to the strong degeneracy of this problem, the results are in coherence with those obtained for the Landau problem. Finally, we consider the case of a transition from a normal MCE to an inverse one and back to normal as a function of temperature. This is due to the competition between the diamagnetic and paramagnetic response when the electron spin in the formulation is included.

Both polycrystalline and single-crystal films of iron-substituted strontium titanate, $\mathrm{Sr}({\mathrm{Ti}}_{0.65}{\mathrm{Fe}}_{0.35}){\mathrm{O}}_{3-\delta }$, prepared by pulsed laser deposition, show room-temperature magnetism and Faraday rotation, with the polycrystalline films exhibiting higher saturation magnetization and Faraday rotation. The magnetic properties vary with the oxygen pressure at which the films are grown, showing a maximum at pressures of approximately $4\mu \mathrm{Torr}$ at which the unit-cell volume is largest. The results are discussed in terms of the oxygen stoichiometry and corresponding Fe valence states, the structure and strain state, and the presence of small-volume fractions of metallic Fe in single-crystal films grown at the optimum deposition pressure. Integration of magneto-optical polycrystalline films on an optical-waveguide device demonstrates a nonreciprocal phase shift.

The crystal structure, magnetic anisotropy and magnetoelasticity of epitaxial SrTi(0.87)Fe(0.13)O(3-δ) (STF13) and SrTi(0.65)Fe(0.35)O(3-δ) (STF35) films grown on (001), (011), and (111) oriented SrTiO(3) substrates were investigated. The films grew with compressive in-plane strain and underwent tetragonal, monoclinic, and rhombohedral distortions on the (001), (011), and (111) substrates, respectively. All samples showed room temperature magnetic hysteresis loops with strong out-of-plane anisotropy. The resulting magnetoelastic anisotropy was an order of magnitude greater than the magnetocrystalline and shape anisotropies. Magnetoelastic coefficients of B(1) =- 6.7 × 10(6) and B(2) =- 28 to -26 × 10(6) erg cm(-3) for STF13 and B(1) =- 2.0 × 10(6) and B(2) =- 5.4 to -3.9 × 10(6) erg cm(-3) for STF35 were determined from the magnetic anisotropy and lattice strain, corresponding to magnetostriction constants of λ(100) = 2.09 × 10(-6) and λ(111) = 7.68 × 10(-6) for STF13, and λ(100) = 0.62 × 10(-6) and λ(111) = 1.07 × 10(-6) for STF35.