将Ag_2O与La_(0.67)Ca_(0.25)Sr_(0.08)MnO_3均匀混合经高温烧结后形成La_(0.67)Ca_(0.25)Sr_(0.08)MnO_3/xAg两相复合体系.随Ag掺入量的增加,样品的电阻率明显下降,磁化强度有小量下降,T_c及电阻率的峰值温度T_p没有明显变化.304 K温度下,从x=0.25样品中得到最大磁电阻效应,磁电阻比约为41%,分别是La_(0.67)Ca_(0.25)Sr_(0.08)MnO_3和La_(0.67)Sr_(0.33)MnO_3样品的1.6及10倍.磁电阻的本征效应和传导电子在界面处的自旋相关散射作用是产生室温下增强磁电阻效应的主要原因.结果说明,利用离子的掺杂效应调整居里温度到室温附近,再结合金属/钙钛矿复合体系界面属性丰富的特性来制备庞磁电阻材料是提高室温磁电阻有效的途径,这对应用研究具有十分重要的意义.
The composite of La_(0.67)Ca_(0.25)Sr_(0.08)MnO_3/xAg was prepared by calcining the mixture of La_(0.67)Ca_(0.25)Sr_(0.08) MnO_3 and Ag_2O powders.With increasing the dopant amount of Ag,resistivity of the sample decreased obviously,and the magnetization decreased slightly,while both T_c and T_p(the peak resistance temperature)almost kept unchanged.At 304 K,the maximum magnetoresistance (MR)effect(41%)Was obtained for the sample with x=0.25,which was 1.6 times and 10 times bigger than that of La_(0.67)Ca_(0.25) Sr_(0.08)MnO_3 and La_(0.67)Sr_(0.33)Mn0_3 samples.The enhancement of MR effect at room temperature was mainly related to the coexistence of intrinsic MR properties and the spin dependent scattering of conduction electrons at the interfaces.These results indicated that it was an effective way to improve the magnetoresistance effect in perovskite at room temperature by using the ion-doping effect to adjust the Curie temperature to room temperature,combined with the plenty characteristics at the interface of metal/perovskite composite.
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