We investigated the magnetoelectric properties of Cr2O3/Co all-thin-film exchange coupling system with Cr spacer layer. In this system, significantly small coercivity (Hc < 50 Oe) was obtained by the Cr spacer layer insertion between Cr2O3 and Co layers. Owing to the small Hc, exchange bias field, Hex, larger than Hc was achieved. It enabled us to observe magnetization switching at a zero magnetic field, when Hex was reversed by magnetoelectric effect of Cr2O3 layer. Finally, we demonstrated the isothermal magnetoelectric switching of magnetization in the Cr2O3/Cr/Co all-thin-film system. By changing the direction of the electric field during the isothermal magnetoelectric switching process, both Hex and magnetization at a zero magnetic field were reversed back and forth, i.e., isothermal magnetization switching by an electric field was achieved.
Neutron-diffraction measurements were made on an ordered Mn3Ir single crystal in a wide temperature range up to 1030 K. The ordered Mn3Ir alloy was found to maintain an antiferromagnetic (AF) triangular spin structure up to the Néel temperature TN=960±10 K. The lattice parameter a shows a continuous change in the temperature range including TN. In contrast to the isostructural ordered Mn3Pt alloy, these observations indicate that an AF–AF phase transition is absent in the ordered Mn3Ir alloy.
A complex new magnetic refrigerant, suitable for the ideal Ericsson cycle, has been investigated. Above ∼15 K it is necessary to use ferromagnets as a magnetic refrigerant. However, temperature variation for the magnetic entropy change in a homogeneous ferromagnet is not suitable for the Ericsson cycle. The present paper verifies, from theoretical analysis, that a complex ferromagnetic material, for instance, (ErAl2)0.312(HoAl2)0.198 (Ho0.5Dy0.5Al2)0.490, has the most suitable characteristics for the ideal Ericsson cycle, including two kinds of isomagnetic field processes. On the basis of the above consideration, a sintered layer structural complex has been prepared, composed of three kinds of RAl2.15 layers, where R’s are rare-earth atoms. From specific heat measurements made on this complex, its entropy and entropy change have been determined. It has been concluded that the complex magnetic material is the most hopeful refrigerant for the Ericsson cycle.
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