Study Of Magnetism And Transport Property Of Perovskite La_1-xNa_xMn_1-yFe_yO₃

Since the discovery of the colossal magnetoresistance (CMR) in the perovskite, which has attracted the attention of the scientic community due to the application foreground and the basic study merits, and perovskites become the focus of spin-electronic and condensed matter physicsOwing to many interesting properties such as magnetic, transport properties. the perovskite have abroad merits to study and latency application merits. In our paper, we study the series of La_1-xNa)xMn_1-yFeyO₃, when x=0.25, y=0, the ratio of Mn³⁺/Mn⁴⁺ of our sample is 1:1, the charge ordering (CO) state may be observed. In this paper, we first study the substitution of alkali metal ions Na⁺ in A site, and at the same time the substitution of Fe³⁺in B site. The analysis of the x-ray powder diffraction pattern shows the formation of homogeneous single-phase compound with rhombohedrally distorted perovskite structure. Because the radius of La³⁺ and Na+ is comparatively, the radiu of Na+ is 113 pm, La3+ is 117.2 pm, after the substitution of A site, the radius of A site is changed and the angle of the bond Mn⁴⁺-O-Mn⁴⁺ is also changed, the angle excurses the original 180°, but this affects a little on the Tc. After the substitution of the B site in La_0.75Na_0.25Mn_1-yFeyO₃, the double-exchange has been impacted and increases other interaction;The substitution of B site or the vacancy of cation, increases the effect of dispersion of transfer electron, and makes the e_g local, weakens the double-exchange, decreases the Curie Temperature, resistivity are increased and CMR are also affected. we also study the different x(=0.17, 0.25) with the same y(=0.05), find that different substitution of x changes the average size of A site, so the magnetic transport properties be affected. In our paper, we get some new results, which are not be found by the other...