Various transition-metal magnetic materials have been investigated from basic and practical viewpoints. The concentration dependence of the Néel temperature TN of Cr-based alloys is complicated. Cr-Si and Cr-Fe antiferromagnetic alloys show Invar characteristics in the ternary alloys. Fe-based amorphous alloys exhibit weak ferromagnetic properties, resulting in remarkable magnetovolume effects. The icosahedral quasicrystals containing Mn show a spin-glass behavior, in a similar manner as those of amorphous counterparts. Itinerant-electron metamagnetic transition occurs in La(FexSi1-x)13, accompanied by many drastic change in magnetic and elastic properties. These drastic changes are practically useful in the field magnetic refrigeration and linear magnetostriction. The magnitude of TN of Mn-based γ-phase is increased by addition of Ir, Ru, Rh and the spin structures change, depending on temperature and composition. Several kinds of L10-type Mn alloys have a high value of TN with a large magnetocrystalline anisotropy. The shift of the exchange-bias field for the collinear spin structure in L10-type phase is induced by spin frustration. L21- and B2-type Co2CrGa metallurgical stable alloys exhibit a high spin polarization. Several kinds of L21-type and B2-type alloys show a large ferromagnetic shape memory effect associated with twin-boundary motions.
We investigated the synthesis conditions and magnetic properties of non-magnetic-ion-substituted Ca-based hexagonal ferrites, Ca0.8La0.2Fe8.0−2xMgxTixO19−σ (x = 0.1–3.5) and Ca0.8La0.2Fey−xAlxO19−σ (x = 1.0–5.0, y = 8.0–10). We found that Mg-Ti-substituted Ca-based M-type ferrites formed at x = 0.1 and 0.2 at above 1225ºC. The sample at x = 0.1 showed the crystallographic single phase of M-type ferrite. The minimum Curie temperature of the Mg-Ti-substituted samples was 367ºC. Also, we found that the Al-substituted Ca-based M-type ferrites had the main phase of M-type ferrite in all samples. As the amount of substituted Al increased, the saturation magnetization and the Curie temperature decreased, and the coercivity increased. As the amount of substituted Al increased by Δx = 1, the Curie temperature decreased by ΔTC = 50–70ºC. Al-substituted samples of x = 1.0 and 2.0 sintered at 1300ºC had the single phase of M-type ferrite.
Thin Films, Fine Particles, Multilayers, Superlattices
Fe-Co and Fe-Co-B alloy films of 40 nm thickness are prepared by sputtering on MgO(001) single-crystal substrates using alloy targets of (Fe0.7Co0.3)100–xBx (x = 0, 5, 10, 15 at. %) by varying the substrate temperature from room temperature (RT) to 600 °C. The film structure is investigated by reflection high-energy electron diffraction and out-of-plane, in-plane, and pole-figure X-ray diffractions. Preparation condition of epitaxial film is found to depend on the B content and the substrate temperature. Epitaxial (Fe0.7Co0.3)100–xBx films are obtained at the investigated temperatures for the B contents lower than 5 at. %, whereas films with the B contents of 10 and 15 at. % grow epitaxially at temperatures higher than 400 and 600 °C, respectively. Single-crystal films of bcc(001) orientation are formed at temperatures higher than RT, 200, 400, and 600 °C for the B contents of 0, 5, 10, and 15 at. %, respectively. As the substrate temperature decreases, the epitaxial films with B contents of 5–15 at. % tend to involve four types of bcc(122) variant whose orientations are rotated around the film normal by 90° each other. The (Fe0.7Co0.3)90B10 film deposited at RT and the (Fe0.7Co0.3)85B15 films deposited at temperatures from RT to 200 °C are found to be consisting of bcc polycrystal and amorphous, respectively. The structure is thus determined to vary in the order of bcc(001) single-crystal => bcc(001) and bcc(122) epitaxial crystals => bcc polycrystal => amorphous with increasing the B content and with decreasing the substrate temperature. The lattices of single-crystal Fe-Co (x = 0 at. %) and Fe-Co-B (x = 5–15 at. %) films are respectively expanded along the in-plane and the perpendicular directions. The single-crystal Fe-Co films show in-plane magnetic anisotropies with the easy magnetization directions of bcc and bcc, which is reflecting the magnetocrystalline anisotropy of bulk bcc-Fe70Co30 alloy. On the contrary, the single-crystal Fe-Co-B films show almost isotropic in-plane magnetic properties and weak perpendicular anisotropies, which is possibly caused by an influence of lattice deformation along the perpendicular direction.