Lanthanum manganites and other giant-magnetoresistance magnetic conductors
Institute for High Pressure Physics, Russian Academy of Sciences, Troitsk, Moscow, Russian Federation
A review is given of crystallographic, magnetic and electric properties of lanthanum manganites and related materials with a giant magnetoresistance (GMR). An analysis of experimental data for partially substituted manganites shows that if the spontaneous magnetic moment is unsaturated, the material is being in a phase-separated ferro-antiferromagnetic state. One possible GMR mechanism consists in a change of such a state under the magnetic field. If the magnetic moment of these materials is saturated, they display a resistivity peak in the vicinity of the Curie point. It is caused by the interaction of the charge carriers with spatial fluctuations of the electric potential and local magnetization. Suppression of this peak by the magnetic field leads to a GMR in ferromagnetic conductors.