The magneto-transport properties are investigated in metamagnetic CoMnSi 0.88 Ge 0.12 alloy. By applying a magnetic field or increasing temperature, a metamagnetic phase transition from antiferromagnetic to ferromagnetic is observed in this alloy. Around the metamagnetic phase transition, CoMnSi 0.88 Ge 0.12 alloy exhibits a large and negative magnetoresistance effect (∼32%) under a magnetic field of 20 kOe (1 Oe = 79.5775 A/m), which is ascribed to the spin-dependent scattering of conduction electrons.

A series of polycrystal bulk samples of (La1-yTby)2/3Sr1/3MnO3(x=0,0.05,0.15,0.20,0.25,0.33,0.4,0.5,0.6,1.0) have been prepared. Their microstructrues, magnetization M, resistance R as well as magnetoresistance (MR) have been systemically studied in the temperature range 10K≤T≤420K. The ferromagnetic transition temperature of the samples TC decrease with the increase y. For each sample, R have peak values at a temperature close to TC. The peak values of R increase rapidly with increasing y. At the sample (y=0.40), a colossal magnetoresistance up to 900% has been observed on the temperature 170K.

Pr(Fe1-xCox)2 ribbons have been prepared by melt-spinning method. Their structure, magnetic properties and thermal stability are investigated. It is found that Pr(Fe,Co)2 cubic Laves phase can form only when x≥0.2 at wheel speed of 45m/s. For Pr(Fe0.6Co0.4)2 alloy, at wheel speed of 30m/s, the ribbon consistes of a mixture of Pr2(Fe,Co)17, Pr(Fe,Co)2 and rare earth-rich phase. Almost Pr(Fe0.6Co0.4)2 compound a small amount of amorphous phase is observed at wheel speed up to 45m/s. Pr(Fe0.6Co0.4)2 compound becomes unstable above 770℃. The resub-bonded Pr(Fe0.6Co0.4)2 nanocrystalline compound which is obtained at wheel speed of 40m/s combines high magnetostriction (λ∥-λ⊥=140×10-6), with significant magnetic coercivity, iHc=398kA/m.

A series of bulk (La1-xPrx)2/3Sr1/3MnO3 polycrystaline samples were prepared by sol-gel technique and the electrical, magnetic properties and magnetostriction effect were studied. At low temperatures, the magnetostriction was mainly about linear magnetostriction and saturated at low magnetic field, and the saturation field decreased with decreasing Pr content. At x=0.3, we found maximum value of -90×10-6.

A series of polycrystaline bulk (La1-xRx)2/3Sr1/3MnO3(R=Sm,Tb) over a wide composition range were prepared by two different techniques, and their structure nd magnetostriction effect were studied carefully at room temperature. The X-ray diffraction pattern indicated that the structure of samples transformed from rhombohedral type to orthorhombic phase with decreasing R contents. The sample, composition near the transformation point, had the maximum value of magnetostriction. The magnetostriction may come from the exchange magnetostriction in the samples at room temperature.