摘要:
基于多种实验手段和能带计算的方法,对四元合金Fe_2Co_（1-x）Cr_xSi的晶体结构、磁性、输运性质及能带结构进行了研究.研究发现,随着Cr的增加,合金Fe_2Co_（1-x）Cr_xSi保持了高度有序结构,逐渐从Hg_2CuTi结构的Fe2CoSi过渡到L2_1结构的Fe_2CrSi;由于次晶格网络的破坏,居里温度逐渐下降;系列合金的分子磁矩呈现线性下降,符合半金属特性;剩余电阻比率与原子占位有序程度密切相关,呈现两端大、中间小的特点.在Cr替代Co的过程中,材料半金属能隙逐渐打开,表现半金属特征.同时费米能级从Fe_2CoSi半金属能隙的价带顶上移至Fe_2CrSi能隙的导带底.最大的能隙宽度出现在x=0.75处,这表明四元合金有可能成为具有更高自旋极化率和更强抗干扰能力的自旋电了学材料.
Abstract:
The structural,the magnetic,the transport and the half-metallic properties of quaternary Heusler alloy Fe_2Co_（1-x）Cr_x Si are investigated. The studies of X-ray diffraction and temperature dependence of magnetization reveal that Fe_2Co_（1-x）Cr_x alloy always maintains a high degree of order,while the Curie temperature decreases gradually with the increase of Cr concentration x.Importantly, the lattice constant and the saturation magnetic moment of Fe_2Co_（1-x）Cr_x alloy follow the Vegard law and half-metallic Slater-Pauling rule,respectively.Based on the band structure calculation,Fe_2Co_（1-x）Cr_x alloy keeps a 100%spin polarization and Fermi level moves from the top of valence band to the bottom of conduction band,depending on Cr concentration x.Our results indicate that quaternary Fe_2Co_（1-x）Cr_x Heusler alloy is a promising robust half-metallic candidate for spintronics applications.
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