Magnetic and Transport Properties Of
نویسنده
چکیده
After the discovery of the high-Tc superconducting oxides, many strongly correlated 3d electron systems have been reinvestigated. Recently, perovskite-type manganese oxides (R,A)MnO3 have been studied extensively. The above group of materials exhibit colossal magnetoresistance (MR) at the carrier doped region, which is interesting not only from the standpoint of strongly correlated systems but also from application. Under appropriate hole doping, the system becomes a ferromagnet which is explained by a double-exchange mechanism [1, 2]. Transport properties for filling-controlled single crystals of La1−xSrxMnO3 have been investigated systematically [3, 4]. It has been made clear that the resistivity is controlled by the magnetization of the system. In either case of applying external magnetic field or lowering the temperature below the Curie point, the resistivity behaves universally as a function of induced or spontaneous magnetization. In the small magnetization region, the universal scaling function is given by ρ(M)/ρ(0) = 1 − C(M/Msat) , where ρ(M) is the resistivity and ρ(0) is its zero-field value. Here M is the magnetization while Msat is its saturated value. This experimental fact shows that the magnetism and the transport properties are strongly correlated. The experimental data also show that the coefficient is C ∼ 4 at x ∼ 0.175, and the value of C decreases as the hole concentration x is increased. In this paper, we investigate the mechanism of the colossal MR responces in this family of manganese oxides.
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