钙钛矿型锰氧化物(La_(0.8)Eu_(0.2))_(4/3)Sr_(5/3)Mn_2O_7的磁性和电性研究  

Magnetic and transport properties of bilayered perovskite manganites(La_(0.8)Eu_(0.2))_(4/3)Sr_(5/3)Mn_2O_7

作　　者：万素磊 何利民[1] 向俊尤 王志国[1] 邢茹[1] 张雪峰[2] 鲁毅[1] 赵建军[1] 

机构地区：[1]内蒙古科技大学包头师范学院物理科学与技术学院,包头014030 [2]内蒙古科技大学,内蒙古自治区白云鄂博矿多金属资源综合利用重点实验室,包头014010

出　　处：《物理学报》2014年第23期328-332,共5页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:11164019);内蒙古自治区科学基金(批准号:2011MS0108;2011MS0101);内蒙古自治区高等学校科学研究基金(批准号:NJZZ11166;NJ10163;NJZY12202)资助的课题~~

摘　　要：采用传统固相反应法制备钙钛矿型锰氧化物(La0.8Eu0.2)4/3Sr5/3Mn2O7多晶样品,X-射线衍射分析表明,样品(La0.8Eu0.2)4/3Sr5/3Mn2O7结构呈现良好的单相.通过磁化强度随温度的变化曲线(M-T)、不同温度下磁化强度随磁场的变化曲线(M-H)和电子自旋共振谱发现:在300 K以下,随着温度的降低,样品先后经历了二维短程铁磁有序转变(T2D C≈282K)、三维长程铁磁有序转变(T3D C≈259K)、奈尔转变(T N≈208K)和电荷有序转变(T CO≈35K);样品(La0.8Eu0.2)4/3Sr5/3Mn2O7在T N以下,主要处于反铁磁态;在T3D C达到370 K时,样品处于铁磁-顺磁共存态,在370 K以上时样品进入顺磁态.此外,分析电阻率随温度的变化曲线(ρ-T)得到:样品在金属-绝缘转变温度(T P≈80K)附近出现最大磁电阻值,其位置远离T3D C,表现出非本征磁电阻现象,其磁电阻值约为61%.在T CO以下,电阻率出现明显增长,这是由于温度下降使原本在高温部分巡游的e g电子开始自发局域化增强所致.通过对(La0.8Eu0.2)4/3Sr5/3Mn2O7的ρ-T曲线拟合,发现样品在高温部分的导电方式基本遵循小极化子的导电方式.Samples of（La0.8Eu0.2）4/3Sr5/3Mn2O7 were prepared by solid state reaction method. X-ray diffraction patterns indicated that the sample shows no any asymmetry and no any trace of secondary phase. The magnetization curve as a function of temperature（M-T）, the magnetization versus magnetic field（M-H） at different temperatures, and the electron spin resonance spectrum have been detected. The magnetization measurement reveals that with lowing temperature, all of the samples undergo a complex magnetic transition. They transform from the two-dimensional short-range ferromagnetic order at T2 D C≈ 282 K, and enter the three-dimensional long-range ferromagnetic state at T3 D C≈ 259 K. Then they step into the antiferromagnetic state at T N ≈ 208 K and enter electric charge temperature order at T CO≈ 35 K. The antimagnetic phase is found in the sample（La0.8Eu0.2）4/3Sr5/3Mn2O7 below T N. When T3 D C= 370 K, the paramagnetic phase and antimagnetic phase co-exist. When T3 D C is above 370 K, only paramagnetic phase exists in the sample. Besides, through electrical resistivity versus temperature curve ρ-T, the sample shows the maximum magnetization electrical resistivity when metal-insulator transition temperature is reached T P ≈ 80 K, T P being far from T3 D C. And the transition shows the phenomenon of intrinsic magnetization electrical resistance, MR ≈ 61%.The resistance begins to increase below T CO. Because of the lowing temperature, the itinerant electron e g becomes increasingly spontaneously localized. One can see from the fitted ρ-T curves that（La0.8Eu0.2）4/3Sr5/3Mn2O7 in high temperature range is in accordance with the small polaron mode range hopping conduction.

关 键 词：磁性 电性 金属-绝缘转变温度 电子自旋共振 

分 类 号：O611.3[理学—无机化学]