Single-crystal Fe16N2 films have been grown epitaxially on Fe(001)/InGaAs(001) and InGaAs(001) substrates by molecular beam epitaxy (MBE). Saturation flux density Bs of Fe16N2 films has been demonstrated to be 2.8–3.0 T at room temperature, which is very close to the value obtained by Kim and Takahashi using polycrystalline evaporated Fe–N films. Temperature dependence of Bs has been measured. Bs changed with temperature reversibly up to 400 °C, while beyond 400 °C, Bs decreased irreversibly. X-ray diffraction showed that Fe16N2 crystal is stable up to 400 °C, while beyond 400 °C, Fe16N2 dissolves into Fe and Fe4N, and also some chemical reactions between Fe16N2 and the substrate occurs. This caused the temperature dependence of Bs mentioned above. From the temperature dependence of Bs up to 400 °C, the Curie temperature of Fe16N2 is estimated to be around 540 °C by using the Langevin function. The above mentioned Bs of 2.9 T at room temperature and 3.2 T at −268 °C corresponded to an average magnetic moment of 3.2μB per Fe atom and 3.5μB, respectively. These values of the magnetic moment of Fe atoms are literally giant, far beyond the Slater–Pauling curves. The origin of the giant magnetic moment has been discussed based on the calculation carried out by Sakuma. However, there was a significant disagreement between experimental values and calculated ones, so the origin remained to be clarified. Also, magneto-crystalline anisotropy of Fe16N2 films has been investigated.
Fe-N films with thicknesses of 70–1000 Å were deposited by MBE onto Fe films which were epitaxially grown onto GaAs(100) substrates. Without the Fe layer, epitaxially grown Fe-N films could not be obtained due to a reaction between Fe-N and GaAs. TEM observations and x-ray diffraction patterns showed that the epitaxially grown Fe-N films consist of Fe16N2 and Fe, and that crystal orientation is Fe16N2 (001)//Fe(110). It was found that the saturation magnetic flux density (Bs) increases as the thickness of the Fe-N films decreases. This is because the volume ratio of Fe16N2 in the Fe-N films increases with decreasing Fe-N film thickness. The maximum value for Bs is 2.66 T, and the volume ratio is 85%. These results indicate that Fe16N2 has a high saturation magnetic flux density of 2.8–3.0 T.
Y-Ba-Cu-O thin films were prepared by an RF magnetron sputtering technique. When annealed at temperatures between 920°C and 1000°C the crystal structures of these films are orthorhombic, while when annealed at 1010°C the structures are tetragonal. Superconductivity can be observed for the orthorhombic films. Their critical temperature (T c) of superconducting becomes higher as the a-axis becomes shorter, and is independent of the b-axis value.
YBa2Cu3O y (superconductor)/La0.7Ca0.3MnO z (magnetic material)/YBa2Cu3O y (superconductor) trilayered-type junctions were prepared on MgO(100) single-crystal substrates, and the current-voltage characteristics were examined. The top and bottom YBa2Cu3O y layers were 200 nm thick, and the La0.7Ca0.3MnO z layer was 20, 30, 50 or 100 nm thick. A supercurrent was observed through all the La0.7Ca0.3MnO z layers, even the thickest one. Further investigation showed that a supercurrent could he observed through the 500-nm barrier layer.
normalZnO‐B2O3‐SiO2 glasses of different compositions were prepared and the surface charges in glass/silicon systems in which these glasses were used, were studied by measuring the capacitance‐voltage curves of metal‐glass‐silicon capacitors. The effects of glass film thickness, glass composition, and conductivity (n‐and p‐types) of silicon substrates on surface charges in glass/silicon systems were investigated. The surface charge density of n‐type silicon changed in the negative direction with increasing glass film thickness and became constant with a thickness of more than 20 μm. The more negative the glass charge, the lower was its surface‐state density. The surface‐charge density of glass coated n‐type and p‐type silicon substrates were found to be linearly related. The surface charge density of mixed glasses with different surface charge density was also investigated.
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