Cr-Co-Ga Heusler合金新材料探索和物性研究

通过实验和计算研究了从Co₂CrGa到Cr₂CoGa一系列渐变成分合金(Co_50-xCr_x+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Co_{2 关键词： CrCoGa Hesuler合金 KKR-CPA-LDA计算}

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

The crystal structure, magnetism and transport properties of a series alloys from Co2CrGa to Cr2CoGa (Co_50-xCr_x+25Ga₂₅, 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 3.06μ_B 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 0.60μ_B to 0.21μ_B 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.