Elastic-strain mechanisms for the influence of temperature, magnetic field, and pressure on the resistive and magnetic properties of magnetic semiconductors

摘要

An analysis is made of the results of studies of the variation of the resistivity of a bulk polycrystalline sample of La{sub}0.56Ca{sub}0.24Mn{sub}1.2O{sub}3 under the influence of temperature (T), pressure (P), and magnetic field (H) and a study of the variation of the magnetostriction in single-crystal LaMnO{sub}3 as a function of T and H. It is found that the peaks of the magnetoresistive, baroresistive, and baromagnetoresistive effects occur at the same temperature, which is independent of magnetic field and pressure and corresponds to the temperature T{sub}(ms) of the metal-semiconductor phase transition in the absence of magnetic field and pressure. "Cooling" and "heating" effects of pressure and magnetic field are detected, and an equivalency of the influence of T, P, and H on the resistivity of the polycrystalline sample and of T and H on the magnetostriction of the single-crystal LaMnO{sub}3 is observed. The linearity of the shifts of the T{sub}(ms)(P) and T{sub}(ms)(H) peaks in the resistive properties of La{sub}0.56Ca{sub}0.24Mn{sub}1.2O{sub}3 is demonstrated and also the linearity of H{sub}g(T) in the magnetic properties for the example of the changes in the hysteresis of the magnetostriction in the LaMnO{sub}3 single crystal. The role of the regularities that obtain for an elastic-strain mechanism for the influence of T, P, and H on the magnetic and resistive properties and phase states is revealed and explained. The sign-varying nature of the influence of T, P, and H is established, and its role in the variation of the resistive and magnetic properties is found (magnetic phase transitions). The relationship of the structural, elastic, resistive, and magnetic properties in magnetic semiconductors is established.