双层钙钛矿锰氧化物Nd_(1.15)Tb_(0.05)Sr_(1.8)Mn_2O_7的磁性和电性研究  

A Study on the Magnetic and Electrical Transport Properties of the Double-layered Perovskite Manganites Nd_(1.15)Tb_(0.05)Sr_(1.8)Mn_2O_7

作　　者：武柯含 向俊尤 王志国[1] 万素磊 赵建军[1] 鲁毅[1] 

机构地区：[1]包头师范学院内蒙古自治区高等学校磁学与磁性材料重点实验室,内蒙古包头014030

出　　处：《稀土》2016年第1期128-131,共4页Chinese Rare Earths

基　　金：国家自然科学基金项目(11164019;51562032);内蒙古自然科学基金项目(2011MS0101);包头重点科技发展项目(2015Z2011)

摘　　要：采用传统固相反应法制备双层锰氧化物Nd1.15Tb0.05Sr1.8Mn2O7多晶样品,通过测量样品的X射线衍射谱、磁化强度随温度变化曲线(M-T曲线)以及电阻率随温度变化曲线(ρ-T曲线),对其磁性和电输运性质进行了研究。结果表明,样品随温度的升高先后经历了四个磁转变点:奈尔温度点(TN≈50 K)、电荷有序温度点(TCO≈67 K)、居里温度点(TC≈107 K)和类Griffiths温度点(TG≈275 K)。在低温部分样品处于反铁磁-铁磁共存态,表现出了团簇自旋玻璃行为;在TC到TG温度范围内,样品处于铁磁-顺磁共存态,即存在类Griffiths相;在TG温度以上,样品处于纯顺磁态。其电输运性质表明,随温度的升高,样品的磁电阻率降低,没有发生金属-绝缘转变。通过对115 K^300 K温度范围内的ρ-T曲线拟合发现,样品在高温部分基本遵循三维变程跳跃的导电方式。Polycrystalline samples of double-layered manganite Nd1. 15Tb0. 05Sr1. 8Mn2O7 were prepared by the traditional solid state reaction method. The properties of the crystallographic structure,magnetism and electrical transport of such samples were characterized by x-ray diffraction（ XRD） spectra,temperature-dependent curves of magnetization（ M-T curves） and resistivity（ ρ-T curves）,respectively. Experimental results show that,upon increasing temperature,four successive magnetic transitions points appear in these samples： Neel temperature point at TN≈50K,Charge-order temperature point at TCO≈50K,Curie temperature point at TC≈107K and Griffiths-like temperature point at TG≈275K. At temperatures below TCO,both antiferromagnetic and ferromagnetic clusters exist,displaying indications of cluster spin glass state. In the temperature range of TCTG,coexistence of ferromagnetic and paramagnetic characteristics are observed,which suggests the samples may be in a Griffiths-like phase. Above TG,the samples enter a pure paramagnetic phase. Magnetoresistance decreases with increasing temperature,and no metal-insulator transition is observed in the electrical transport measurements. The fitting to ρ-T curves at 115K-300 K shows that electric conductivity at high temperatures is essentially attributed to three-dimensional variable-range hopping.

关 键 词：锰氧化物 磁性 电输运性质 类Griffiths相 

分 类 号：O482.52[理学—固体物理] O614.33[理学—物理]