Giant and isotropic magnetoresistance as huge as −53% was observed in magnetic manganese oxide La0.72Ca0.25MnOz films with an intrinsic antiferromagnetic spin structure. We ascribe this magnetoresistance to spin-dependent electron scattering due to spin canting of the manganese oxide.

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.

The magnetoresistance (MR) effects of La0.72Ca0.25MnOz (LCMO) magnetic films and LCMO/YBa2Cu3Oy (YBCO)/LCMO trilayered films were studied. The LCMO films have an MR ratio of −4% when applying 1 T at 77 K and this value is independent of the film thickness from 1500 to 4500 Å. In contrast to that, the MR ratio for LCMO/YBCO/LCMO films depends on the thickness of the YBCO layer and is more than 1.5 times as large as that for LCMO films when the thickness of the YBCO layer is less than 2500 Å. These results imply that the magnetic spin interaction between the two LCMO layers may exist through the normal-conductive state YBCO layer.

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