铥掺杂钙钛矿锰氧化物La_(0.7)Sr_(0.3)MnO_(3)的临界行为和磁熵变研究  

Critical Behavior and Magnetic Entropy Change of Thulium-doped Perovskite Manganese Oxide La_(0.7)Sr_(0.3)MnO_(3)

作　　者：周敏[1] 赵建军[1] 金香[1] 邢茹[1] 郑琳[1] 鲁毅[1] Zhou Min;Zhao Jianjun;Jin Xiang;Xing Ru;Zheng Lin;Lu Yi(Key Laboratory of Magnetism and Magnetic Materials at Universities of Inner Mongolia Autonomous Region,Baotou Teachers’College,Inner Mongolia University of Science and Technology,Baotou 014030,China)

机构地区：[1]内蒙古科技大学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：《中国稀土学报》2022年第5期793-804,共12页Journal of the Chinese Society of Rare Earths

基　　金：国家自然科学基金项目(11164019,51562032)资助。

摘　　要：在钙钛矿锰氧化物La_(0.7)Sr_(0.3)MnO_(3)的La位掺杂Tm^(3+),研究掺杂对体系结构、磁性、磁相变附近的临界行为和磁熵变的影响。通过掺杂调节A位平均离子半径,使体系居里温度更趋近室温;利用Kouvel-Fisher方法分析磁转变温度附近的临界行为,La_(0.7)Sr_(0.3)MnO_(3)的临界指数与三维海森堡模型的临界指数非常接近,表明未掺杂时磁相变附近的铁磁耦合为短程有序。掺杂Tm^(3+)后样品La_(0.65)Tm_(0.05)Sr_(0.3)MnO_(3)的铁磁临界指数β趋近于海森堡模型,但顺磁临界指数γ却更接近于平均场理论模型,这可能是受顺磁区域的偶极相互作用影响。同时掺杂Tm^(3+)后,在7 T磁场下的磁熵变值由6.19 J·kg^(-1)·K^(-1)减小到4.99 J·kg^(-1)·K^(-1),但是相对磁制冷能力却由295 J·kg^(-1)增大到353 J·kg^(-1),体系相对磁制冷能力增强的原因是掺杂导致磁熵变温区展宽,这使得掺杂样品具有实现室温磁制冷的潜能。The effects of doping Tm^(3+) ions on the structure,magnetic properties,critical behavior and magnetic entropy change of the perovskite manganese oxide La_(0.7)Sr_(0.3)MnO_(3) were studied.By adjusting the average ionic radius of A site,the Curie temperature of the system is closer to room temperature.Using the Kouvel-Fisher method to analyze the critical behavior near the magnetic transition temperature,the critical exponents of La_(0.7)Sr_(0.3)MnO_(3) is very close to the critical exponents of three dimensional Heisenberg model,indicating that the ferromagnetic coupling of the sample is short-range order.The ferromagneticcritical exponentsβof the polycrystalline sample La_(0.65)Tm_(0.05)Sr_(0.3)MnO_(3) is close to the Heisenberg model,the paramagnetic critical exponentsγhas some deviation from the Heisenberg model,and its value is closer to the mean field model,which may be related to the dipole-dipole interaction in the paramagnetic state.After doping with Tm^(3+) ions,the maximum magnetic entropy changes values decreased from 6.19 to 4.99 J·kg^(-1)·K^(-1),at the magnetic field of 7 T,but the relative magnetic cooling capacity increases to 353 J·kg^(-1) from 295 J·kg^(-1).The reason for the enhanced relative magnetic refrigeration capacity of the system is that the doping leads to the broadening of the magnetic entropy variable temperature region,which increases the magnetic refrigeration temperature range and makes the sample have the potential to achieve room temperature magnetic refrigeration.

关 键 词：稀土 磁性 磁熵变 临界行为 

分 类 号：O482.54[一般工业技术—材料科学与工程] O482.6[理学—固体物理]