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Magnetic tunnel junctions of Co0.9Fe0.1/SrTiO3 (STO)/ La0.7Sr0.3MnO3 (LSMO) with a spin-valve structure having an antiferromagnetic MnIr layer have been fabricated by sputtering. Junction magnetoresistance (MR) behavior and its dependence on the bias voltage are examined for junctions with epitaxial STO barrier formed under different sputtering conditions. Spin dependent transport measurements show that these junctions exhibit spin-valve type MR loops with an inverse (positive) MR of the ratio of 14-22 % at 4.2 K. The inverse MR observed is asymmetric with respect to the bias voltage direction. Stoichiometric STO barrier, as characterized by Rutherford backscattering (RBS) analysis, is found to result in very large asymmetric bias dependence, while the junctions with nonstoichiometric STO barrier exhibit the symmetric bias dependence. Our results suggest that the nonstoichiometry of STO barrier modifies the electronic structures of electrode/barrier interfaces, and thereby reducing the asymmetry of bias voltage dependence of junction MR.

With a use of the epitaxial a-axis thin films of perovskite series Lan-nxCa1+nxMnnO3n+1 (n=2,3, and ∞) with fixed carrier concentration (x=0.3), the transport properties of the series compounds have been examined to be associated with the difference in the number of the MnO2 layers. Results have indicated that a reduction in the number of layers results in systematic changes in the various features. These include an increase in resistivity, a decrease in resistivity peak temperature Tcρ corresponding to the metal-insulator transition, an enhancement of the maximum MR near Tcρ, and an increase in low temperature intrinsic MR. In order to explain the variation in these features with the number of MnO2 layers, it is necessary to take both anisotropie c-axis transfer interaction and two-dimensional spin fluctuation into account.

To clarify the relation between high magnetic permeability and magnetic phases of Fe73.5Cu1Nb3Si13.5B9 ribbons, the process of precipitation was investigated by using the Xray diffraction, DTA, VSM and the Mössbauer spectra at various annealing temperatures. The volume fraction of each magnetic phase was estimated. The sample annealed at 853K which shows maximum permeability is composed of partially ordered Fe3Si(70%), Fe(B) solid solution(10%) and amorphous(20%) phases. The relative permeability of the sample annealed below 853K increases with increasing the volume fraction of both of the Fe3Si partially ordered and the Fe(B) solid solution phases. The relationship between tile permeability and the volume fraction is interpreted by the random anisotropy model.

Magnetic phase diagrams of YBa2 (Cu1–xFex)30y and YBa2 (Cu1–xCox)30y were determined by measuring positive muon spin relaxation and magnetic susceptibility (SQUID).