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A nonequilibrium rapid-quenching method has been used to fabricate NiMnIn and NiMnGa alloys that are chemically and morphologically similar but crystallographically and physically very different. NiMnGa crystallizes in a Ni2In-type hexagonal structure, whereas NiMnIn is a cubic Heusler alloy. Both alloys yield a topological Hall effect contribution corresponding to bubble-type skyrmion spin structures, but it occurs in much lower magnetic fields in NiMnIn as compared to NiMnGa. The effect is unrelated to net Dzyaloshinskii-Moriya interactions, which are absent in both alloys due to their inversion-symmetric crystal structures. Based on magnetic-force microscopy, we explain the difference between the two alloys by magnetocrystalline anisotropy and uniaxial and cubic anisotropies yielding full-fledged and reduced topological Hall effects, respectively. Since NiMnIn involves small magnetic fields (0.02–0.3 kOe) at and above room temperature, it is of potential interest in spin electronics.

The structural features of magnetically anisotropic SmCo5 ribbons prepared by melt spinning have been investigated by means of transmission electron microscopy. It was determined that this kind of SmCo5 ribbons are made up of structural domains, which consist of layered grains regularly packed along the c-axis direction. The c axes of the grains generally lie in the ribbon plane and along the length. The SmCo5 grains are well crystallized in the conventional hexagonal structure (P6/mmm). The properties of grain boundaries either with or without impurity phases have been systematically analyzed.

Magnetically anisotropic Sm1−xGdxCo5 (x=0, 0.2, 0.5) ribbons are produced by conventional melt spinning. The coercivity Hc increases from 5 kOe for x=0 to 11 kOe for x=0.5. Microstructure analyses show that this abnormal change of the coercivity is ascribed to the decrease of the quantity of the 2:7 phase, which serves as a center for a reverse domain. The remanence ratio also increases from 0.80 for x=0 to 0.95 for x=0.5. An energy product of 16 MGOe at room temperature for the Sm0.8Gd0.2Co5 ribbons has been achieved without the need of a complex heat treatment. The temperature characteristic of remanence is substantially improved due to the change of the microstructure arising from Gd substitution.

We have investigated the effect of epitaxial strain on the electrical and magnetic properties of high quality Ca2RuO4 films on LaAlO3 (001) substrates. The films exhibit low temperature itinerant ferromagnetic ground state and significantly suppressed metal-insulator transition due to epitaxial strain. An anomaly in the in-plane resistivity was also observed near the Neel temperature. Symmetry analysis of anisotropic magnetoresistance suggests a phase coexistence of ferromagnetic metal and antiferromagnetic insulator in ground state.