La <sub> 1/2 </ Sub> Of (sr <sub> 1-x </ Sub> Of Ca <sub> X </ Sub>) <sub> 3/2 </ Sub> Of Mno <sub> 4 < / Sub> And Nd <sub> 2-2x </ Sub> Of Ca <sub> The 1 +2 X </ Sub> Mn

The chapter one, two and three: Reviewed the physical characteristics of the ABO₃ type manganese oxide. Summarized the current research results and the recent progress of this system. And the anticipation and existence solution's question has been given the explanation. Introduced the sample preparation process, experimental methods, the principle of Rietveld method and the basic steps of fitting.The chapter four and five: Polycrystals of single-layered perovskite La_1/2(Sr_1-xCa_x)_3/2MnO₄ and Nd_2-2xCa_1+2xMn₂O₇ were prepared by solid-state reactions. With the Rietveld-Method, the samples' XRD pattern was fitted by the program FULLPROF. The compounds show the space group I4/mmm at the room temperature. The temperature dependence of the electrical transport properties and magnetic properties were measured. The results show:The resistivities of La_1/2Sr_1-xCa_x)_3/2MnO₄ samples increase with the decrease of temperature. It shows the insulator behavior within testing temperature range. The resistivities of samples decrease with increase of doping level. Transport properties below T_CO can be explained quite well based on the Variable Range Hopping Model. In the high temperature region, the series of samples show the paramagnetism. The Charge -Orbital- Spin order transition happens near 200 - 235K, and the COS order has been extended to low temperature. The susceptibility of sample x = 0.3 increases abruptly due to the spin-glass transition.The sample of Nd_1.2Ca_1.8Mn₂O₇ shows the ferromagnetism in the low temperature. Magnetization is 1.4μ_B. With the rise of temperature, the sample undergoes the FM - PM transition near 120 K. The resistivity of the Nd_1.2Ca_1.8Mn₂O₇ becomes lower with the rise of temperature. It shows the insulator behavior within testing temperature range. The sample of NdCa₂Mn₂O₇ shows the antiferromagnetism in the low temperature range because it exists the orbital order and charge order. With the rise of the temperature, the orbital order and charge order were broken. The sample shows the AFM - PM transition near 125 K. The activation energy E_ac[≡d(lnρ)/d(1/T)] of NdCa₂Mn₂O₇ was calculated with the temperature dependence of resistivity. The critical temperature T_CO for the charge ordering transition was 125 K.