(La2/3Ca1/3)(Mn(3-x)/3)Fex/3)O3体系磁电阻行为的研究

通过系统地测量（La_2/3Ca_1/3）（Mn_{（3-x）／3}Fe_x／3）O₃（x＝0、0.1、0．2、0．3的体系样品的电阻率-温度关系以及一定温度下磁电阻率与磁场的关系，发现随x的变化其磁电阻率峰和电阻率峰均发生位移，磁电阻率峰值增大，并伴生磁电阻率峰展宽效应．作者认为由于Fe的替代，引起体系中Mn³⁺／Mn⁴⁺比率及磁矩的变化，加之外场对磁有序结构的调制作用，从而影响了Mn³⁺－O^－Mn⁴⁺的双交换作用，最终导致磁电阻行为发生变化．

Magnetoresistance Behavior of (La2/3Ca1/3)(Mn(3-x)/3Fex/3)O3 System

The temperature dependence of electrical resistance and magnetoresistance as well as field dependence of magnetoresistance at fixed temperature of the (La_2/3Ca_1/3)(Mn_(3-x)/3Fe_x/3)O₃ (x=0, 0.1, 0.2, 0.3) system were systematically measured . It was found that when x increases, both the peak of the electrical resistivity and the peak of magnetoresistance move to lower temperature. However the giant magnetoresistance (GMR) is increased and its cusp is broadened by Fe substitution. The authors suggested that the variation of the proportion of Fe³⁺ ions leads to the changes of the ratios of Mn³⁺ to Mn⁴⁺ and magnetic moments while external magnetic field modulates the magnetic ordered structure, so affects the ferromagnetic double exchange effect of the Mn³⁺--O--Mn⁴⁺. Finally, such phenomenon changes the behavior of magnetoresistance.