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From our previous studies, it has been found that the Fe-Pb-O granular films which have been adequately annealed exhibit an enhanced tunneling magnetoresistance effect (TMR). The TMR effect is about 10% at room temperature, which can be claimed as the maximum value ever detected so far. In this report the TMR effect of Fe-Pb-O granular films from different annealing time have been investigated. The Mossbauer spectrometer was used to collect the information of Fe magnetic microstructure. It has been found that the tunneling barrier from the magnetic compound formed between a-[Fe.sup.2][O.sub.3] and PbO plays an important role in obtaining large TMR effect. And the non-magnetic Fe-Pb-O compounds which exist on the surface of iron granules as a thin layer and grow with annealing time seem to decrease TMR effect.

The magneto-transport properties of the granular [Fe.sub.0.5][([Al.sub.20][O.sub.3]).sub.0.5] solids with various film thickness have been investigated. The temperature dependence of the resistivity shows that all samples follow a tunneling type equation [Rho](T) =[Rho]exp[([T.sub.0]/T).sup.1/[Alpha]] with [Rho] [approximately equal to] 0.0 [similar to] 1 [ohms]cm at 300K and [Alpha]=2. The results of magneto-resistance at 300K indicate that the value is about 4.5% for thick films. It increases slowly with decreasing film thickness. At about 150nm, a peak value of TMR is found, which is determined to be 5%. Then TMR drops sharply with further reducing film thickness. It becomes only 3% at t=20nm. At low temperatures, the TMR effect becomes larger and shows similar thickness dependence. However, the values of [T.sub.0] that relate to the geometry of the tunneling barrier show behavior of opposite thickness dependence. A small [T.sub.0] is associated with a large TMR effect. In this report, the correlation of the film microstructure and the TMR effect are discussed in details.

Ultrafine Gd particles in a Cu metallic matrix have been obtained by post-annealing of as-sputtered metastable [Gd.sub.x][Cu.sub.1-x] alloys at temperatures higher than 250 [degrees] C. The results of resistivity measurements show that the resistivities of as-sputtered metastable [Gd.sub.0.2][Cu.sub.0.8] and [Gd.sub.0.3][Cu.sub.0.7] alloys exhibit a resistivity minimum at low temperatures, an indication of the Kondo effect. In addition the temperature of the resistivity minimum rises with the increasing Gd content. Conversely, the resistivity of films after formation of Gd granules levels off at low temperatures. The magnetic results indicate that the metastable GdCu alloys are essentially a spin-glass at low temperature with the transition temperatures at around 3.5-5K. However, magnetization data at 80K shows that the as-sputtered samples contain some small Gd ferromagnetic clusters in the paramagnetic matrix. The magnetic particles of granular films begin to be thermally blocked at [T.sub.B] and become magnetically ordered below [T.sub.B]. Due to larger grain sizes, [T.sub.B] is much higher for x=0.3 than for 0.2. The variation of transport and magnetic properties for samples with different annealing processes are described in detail.

The addition of 2 at% Ta or 1 at% Ti into a (Nd,Dy)-(Fe,Co)-B alloy is very effective in improving room temperature coercivity and thermal stability. The Ta containing alloy showed 30 % higher coercivity value than that of Ta-free alloy at temperatures higher than 100 degrees C. Both Ta and Ti alloying greatly reduced the high temperature reversible losses at temperatures of up to 225 degrees C. They are thus potential in high temperature applications.

The addition of 2 at% Cr or W into a sintered (Nd,Dy)-(Fe,Co)-B alloy is very effective in improving room temperature coercivity and thermal stability. The W-containing alloy showed twice the coercivity value to that of W-free alloy at temperatures higher than 100 degrees C. Both W and Cr alloying greatly improve the high temperature stability. There exists a WFeB precipitate phase in the W-containing alloy. The WFeB phase is platelet with its long axis parallel to c-axis of the 2-14-1 phase. The domain wall pinning at the precipitate phase, as evidenced by the Lorentz microscopy, is the reason of enhanced coercivity of this alloy, particularly at high temperatures.

Magnetic properties of Sm2Fe17Nx and SmFe5Ny with different nitrogen contents were studied. It was found that the magneto-crystalline anisotropy for both Sm2Fe17Nx and SmFe5Ny alloys changes from easy plane to easy axis at x > 0.13 and y > 0.07. The 1:5, 1:3 and alpha-Fe phases coexist in homogenized SmFe5 alloy. Nitrogenation reduces the 1:3 and alpha-Fe phases, and stabilizes the 1:5 phase in SmFe5Ny alloys. The transition in magnetocrystalline anisotropy from easy plane to easy axis for Sm2Fe17Nx and SmFe5Ny alloys is gradual and dependent on nitrogen content.