亚铁磁Heusler合金Mn_2CoGa和Mn_2CoAl掺杂Cr,Fe和Co的局域铁磁结构  

Local ferromagnetic structure in Heusler alloy Mn_2 CoGa and Mn_2 CoAl doped by Cr, Fe and Co

作　　者：张玉洁[1] 李贵江[1] 刘恩克[1] 陈京兰[1] 王文洪[1] 吴光恒[1] 胡俊雄[2] 

机构地区：[1]中国科学院物理研究所,磁学国家重点实验室,北京100190 [2]四川师范大学物理与电子工程学院,成都610068

出　　处：《物理学报》2013年第3期354-360,共7页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:51031004;11174352)资助~~

摘　　要：通过实验和计算的方法研究了Mn2CoMxGa(1-x)和Mn2CoMxAl(1-x)(M=Cr,Fe,Co)掺杂系列合金样品.研究发现,在共价作用的影响下,Fe和Co原子占A位,使被取代的MnA(2.1μB)变成MnD(3.2μB),在最近邻的强交换作用下亚铁磁基体中形成了MnB-CoC-MnD局域铁磁性结构,使分子磁矩的增量最高可达6.18μB.Fe,Co掺杂后建立同样的局域铁磁结构,居里温度的变化趋势却不同.实验观察到Mn2Co(1+x)Al(1-x)中掺杂容忍度高达x=0.64,远高于在Mn2CoGa中(x=0.36)的结果;以及随着Al的减少,合金由B2有序向A2混乱转变等现象,为共价作用对合金结构稳定的影响提供了证据.磁测量中发现Cr掺杂后磁矩增量高达3.65μB以及居里温度快速上升的反常现象,意味着对占位规则的违背.The crystal structures and magnetic properties of Mn2CoMxGa1？x and Mn2CoMxAl1？x （M=Cr, Fe, Co） alloys are investigated through experiment and calculation. Due to the covalent effect, the doped Fe and Co atoms preferentially occupy the A sites. It causes that some MnA （？2.1 μB） atoms become MnD （3.2 μB） and a local ferromagnetic structure of MnB-CoC-MnD is generated in the ferrimagnetic matrix, showing that an increment of molecular moment is as high as 6.18 μB. The achievement of the ferromagnetic structure consumes the exchange interaction energy, consequently, reducing the TC in Fe doping alloys. It is found that the toleration for doping Co in Mn2CoAl reaches up to x=0.64, much more than that in Mn2CoGa （x=0.36）, and the change from ordered B2 to A2 structures along with the decrease of Al content. These observations reveal the importance of the covalent effect in these intermetallic compounds. The Cr doping shows an abnormal increment of molecular moment of 3.65 μB and increases the TC rapidly, which implies that Cr atoms may take an atomic configuration thereby disobeying to the occupation rule.

关 键 词：HEUSLER合金 原子占位 铁磁结构 交换作用能 

分 类 号：O482.5[理学—固体物理]