A Study On The Electrical, Magnetic Transport Properties And Internal Friction Of Electron-doped Manganese Perovskites

The colossal magnetoresistance (CMR) behavior in manganese perovskites has been one of the most frontier objects in the present condensed physics and material science due to its physical properties and its important potential applications on magnetic memories as well as magnetic read/write heads for magnetic disk drives. It may underlie the phenomenon of colossal magnetoresistance (CMR) in hole-doped perovskite manganites studied extensively in recent years. A few studies of electron-doped manganites revealed anomalous magnetic properties and drew attention to these compounds.In the first chapters, the history and the present research situation of colossal magnetoresistance effect have been introduced. We summarized the crystal structure, magnetic and electronic transport properties. In the meanwhile, we generalized the possible origin of colossal effect of perovskite structure manganese oxides and some related physical phenomena.The electrical, magnetic transport properties, magnetoresistance and internal friction of La_0.85Te_0.15MnO₃ have been investigated in chapter two. A ferromagnetic-paramagnetic phase transition is observed in the temperature dependence of magnetization, there are two transitions peak in the temperature dependence of resistivity and the high temperature peak in Curie-temperature T_c corresponding the ferromagnetic-paramagnetic phase transition. There have a internal friction in Metal to Insulator (MI) transition region, and the modulus have been changed.In chapter three, the resistivity and magnetism's transport properties, and internal friction of Ca_1-xY_xMnO₃(02+ for Y³⁺ is accompanied initially by the rise of the ferromagnetic component in magnetization and decreasing resistivity. On further increasing the lanthanide content, the competition between ferromagnetic and anti-ferromagnetic interactions becomes stronger, resulting in peculiar magnetic behavior of electron magnates. Studies on the cooperative Jahn-Teller effect in Ca_1-xY_xMnO₃ by means of frequency internal friction instrument. When the temperature below T_min, the relative modulus AEn varies with the Y³⁺ concentration, it reveals the degree of cooperative Jahn-Teller lattice distortion varies with the Y³⁺ concentration, at X=0.25 the relative modulus AEn reaches the largest, the cooperative Jahn-Teller lattice distortion reaches maximum also.The effect of electric current on the charge-ordered state in Ca_0.5Y_0.5MnO₃ has beeninvestigated in chapter four. It found since electric current effects destroy charge-ordered state, and cause decrease of resistivity. The effect of electric current on the charge-ordered state in Ca0 5Yo 5Mn03 cause the change of modulus and internal friction peak, so it work on the ferromagnetic and anti-ferromagnetic region...