Cr-Co-GaHeusler合金新材料探索和物性研究  

New material exploration and magnetism research on Heusler alloys Cr-Co-Ga

作　　者：钱金凤[1] 冯琳[1] 朱伟[1] 刘恩克[1] 唐晓丹[1] 王文洪[1] 吴光恒[1] 孟凡斌[2] 刘何燕[2] 罗鸿志[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]河北工业大学材料科学与工程学院,天津300130

出　　处：《物理学报》2011年第5期557-561,共5页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:50971130;50971055)资助的课题~~

摘　　要：通过实验和计算研究了从Co2CrGa到Cr2CoGa一系列渐变成分合金(Co50-xCrx+25Ga25,x=0—25)的结构、磁性及输运性质.当Cr不断替代A位Co时,晶体结构逐渐从典型的L21结构过渡到Hg2CuTi结构,晶格常数线性地增大0.69.合金的磁性从Co2CrGa的铁磁性转变为Cr2CoGa的反铁磁状态,分子磁矩从3.06μB线性地降低到接近零磁矩.采用CPA方法的第一性原理计算获得了各个原子磁矩的取向和数据,发现替代进入A位的Cr与原有的B位Cr的原子磁矩大小接近,但形成了很强的反铁磁耦合,破坏了原有的铁磁性;同时C位Co的磁矩发生较大下降,从0.60μB降到0.21μB.将XRD结构分析和磁性测量与CPA计算相结合,确定了Cr2CoGa中存在着约20的原子混乱.值得关注的是,该系列样品的居里温度却并非线性变化,出现了一种"成分中点"现象,合金的电阻率的成分关系和温度关系与之一致.本工作围绕磁性原子的环境变化展开了讨论.The crystal structure,magnetism and transport properties of a series alloys from Co2CrGa to Cr2CoGa（Co50-xCrx ＋25 Ga25,x = 0—25） have been investigated by the experimental and KKR-CPA-LDA calculation methods.Substituting Cr for Co atoms,the crystal structure changes from L21 type to Hg2CuTi structure,which make,the lattice parameters increase about 0.69 linearly.Also,the ferromagnetic coupling turns to anti-ferromagnetic coupling,that makes the magnetic moment linearly decrease from 3.06μB to nearly zero.Through ab initio study of CPA,it has been found that the extraneous Cr atom at the A site couples anti-ferromagnetically with the Cr atom originally situated at B site with a nearly equal magnitude of magnetic moment,and the magnetic moment of Co atoms occupying the C site decreases from 0.60μB to 0.21μB through the whole substituting process.Based on the results of magnetic measurement and calculation,about 20 atomic disorder in the alloy Cr2CoGa has been confirmed,which is consistent with the observation of the X-ray examination.It is interesting that a non-linear＂middle component phenomenon＂has been observed in the composition dependence of both Curie temperature and the electrical resistivity.The related discussions is based on the magnetic environment change surrounding the magnetic atoms.

关 键 词：CrCoGa Hesuler合金 KKR-CPA-LDA计算 

分 类 号：O482.5[理学—固体物理]