DyGa_2和DyGa_(1.8)Cu_(0.2)化合物的结构和磁卡效应  

Crystal Structure and Magnetocaloric Effect of DyGa_2 and DyGa_(1.8)Cu_(0.2) Compounds

作　　者：韩向臻[1] 杜红林[2] 孙凯[1] 刘蕴韬[1] 陈东风[1] 

机构地区：[1]中国原子能科学研究院,北京102413 [2]北京大学物理学院,北京100871

出　　处：《原子能科学技术》2010年第B09期35-39,共5页Atomic Energy Science and Technology

基　　金：国家重点基础研究发展计划资助项目(2010CB833101);国家自然科学基金资助项目(10875007)

摘　　要：利用电弧炉制备了DyGa2和DyGa1.8Cu0.2合金样品。通过X射线粉末衍射方法和测量磁性研究了两种合金的晶体结构和磁性能。研究结果表明:DyGa2和DyGa1.8Cu0.2化合物的晶体结构为P6/mmm六方结构,用少量Cu替代Ga可使晶胞体积变小。DyGa2和DyGa1.8Cu0.2合金的奈尔温度分别为16K和113K,温度低于奈尔温度发生顺磁-反铁磁相变,且相变类型为二级相变。DyGa2在8K温度附近发生变磁转变,为一级相变。DyGa2的最大磁熵变值为7.3J/(kg·K),具有较强的磁制冷能力,约为131J/kg,在5K附近出现-14.9J/(kg·K)的异常负磁熵变,使DyGa2具有了温度自调节功能。掺杂少量Cu将合金的磁制冷温度提高到100K附近,具有很好的磁制冷应用开发潜力。The crystal structures and magnetocaloric effect of DyGa2 and DyGa1.8Cu0.2 compounds were studied by X-ray powder diffraction and magnetic measurements. The main results show that the crystal structures of compounds are hexangular structure with space group of P6/mmm, and the cell volume decreases when Ga atoms are substituted by Cu atoms. The Neel temperatures of DyGa2 and DyGa1.8Cu0.2 are 16 and 113 K, respectively. They are anti-ferromagnetic below Neel temperature, which become paramagnetic near Neel temperature. The kind of this phase transiton is second order phase transition. The M vs. H curves for T≤ 8 K exhibit features that resemble those of a metamagnetic transformation which is first order phase transition. For a magnetic field change of 50 kOe, the maximum values of -ΔSM for DyGa2 is 7.3 J？kg-1？K-1, and cooling power is 131 J？kg-1. The values of -ΔSM for DyGa2 is unconventionally negative （-14.9 J？kg-1？K-1） at about 5 K. The phenomenon can be used in temperature control. A small amount of Cu doping makes the magnetic refrigeration temperatures to about 100 K. They are potential candidates for the practical magnetic refrigeration.

关 键 词：晶体结构 磁卡效应 磁熵变 磁制冷 

分 类 号：O571.56[理学—粒子物理与原子核物理]