La_(8/9)Sr_(1/45)Na_(4/45)MnO_3/0.5x(V_2O_5)复合体系的电输运及磁电阻  

Electric Transport and Magnetoresistance in La_(8/9)Sr_(1/45)Na_(4/45)MnO_3/0.5x(V_2O_5) Composites

作　　者：唐永刚[1,2] 王桂英[1,2] 严国清[1,2] 宋启祥[1,2] 张明玉[1,2] 彭振生[1,3] 

机构地区：[1]自旋电子与纳米材料安徽省重点实验室(培育基地),安徽宿州234000 [2]宿州学院机械与电子工程学院,安徽宿州234000 [3]中国科学技术大学合肥微尺度物质科学国家实验室,合肥230026

出　　处：《硅酸盐学报》2012年第7期1018-1022,共5页Journal of The Chinese Ceramic Society

基　　金：国家自然科学基金(19934003);安徽省教育厅自然科学研究重点项目(KJ2011A259);宿州学院教授(博士)基金(2011jb01;2011jb02)及宿州学院科研平台开放课题(2010YKF04)

摘　　要：用固相反应法制备了La8/9Sr1/45Na4/45MnO3/0.5x(V2O5)(x=0,0.04,0.08,0.12,0.16,0.20)系列样品,通过X射线衍射谱、扫描电子显微镜、电阻率–温度(ρ–T)和磁电阻–温度(RM–T)的关系,研究了样品的电输运性质及RM温度稳定性。结果表明:所有样品表现为从高温区绝缘体导电到低温区金属导电的绝缘体–金属相变,随V2O5复合量增大,绝缘体–金属转变温度Tp向高温移动;V2O5复合量较小(x≤0.08)时ρ–T曲线出现双峰,V2O5复合量较大(x≥0.12)时ρ–T曲线双峰消失;所有样品在低温区随温度降低RM持续增大,表现出低场磁电阻特征,在高温区的本征磁电阻随V2O5复合量增大而逐渐减小;对于x=0.16、0.20的样品,在0.8 T磁场,319～283 K,RM基本保持6.4%和5.8%不变。RM温度稳定性的产生原因可能是表面相引起的隧穿磁电阻与体相引起的本征磁电阻竞争的结果。在高温区体相内部双交换引起的本征磁电阻占优势,在低温区界面的磁无序引起的隧穿磁电阻占优势,最终在中间温区产生不随温度变化的RM。The samples of La8/9Sr1/45Na4/45MnO3/0.5x（V2O5） （x = 0, 0.04, 0.08, 0.012, 0.16, 0.20） were prepared by a solid-state reaction method. The temperature stability of magnetoresistance and electric transport property in the system were investigated via X-ray diffraction （XRD）, scanning electron microscopy, resistivity-temperature （p-T） and magnetoresistance-temperature （RM-T） measurements. The results show that for all the samples, there is a insulator-metal transition from high temperature range to low temperature range. The insulator-metal transition temperature （Tp） shifts to high temperature with increasing V2O5 content. Two peaks appear in the p-T curves of the samples （x≤0.08） with a low V2O5 content, and they vanish in the samples （x ≥0.12） with a high V2O5 content. The magnetoresistance （RM） of the samples increases with decreasing temprerature in the low temperature range, as a characteristic of low-field magnetoresistance effect. The intrinsic magnetoresistance in the high temperature range decreases with increasing V2O5 content. The magnetoresistance of the samples of x = 0.16 and 0.20 in the temperature range of 319-283 K at 0.8 T is 6.4% and 5.8%, respectively. The RM temperature stability may be due to the competition between the tunneling magnetoresistance caused by surface phase and the intrinsic magnetoresistance caused by bulk phase. The intrinsic magnetoresistance in bulk phase caused by double exchange dominants in the high temperature range, and the tunneling magnetoresistance caused by interface magnetic disorder dominants in the low temperature range. The RM does not change with temperature in the middle temperature range.

关 键 词：电输运性质 磁电阻温度稳定性 复合体 钙钛矿锰氧化物 

分 类 号：O482.54[一般工业技术—材料科学与工程]