Heusler合金Fe_2CrGa的磁性与结构

Magnetic property and structure of Heusler alloy:Fe_2CrGa

采用KKR-CPA-LDA方法研究了不同混乱占位时Fe_2CrGa合金基态的电子结构和磁结构.基态能量表明Fe_2CrGa合金更倾向于形成Hg_2CuTi型有序结构,而不是L2_1结构.能态密度(DOS)分析进一步揭示受晶体场影响的磁性原子内部交换作用是使Fe_2CrGa合金形成Hg_2CuTi型有序结构的主要原因.测量了不同热处理所得Fe_2CrGa合金的居里温度和分子磁矩,发现原子占位有序化可以在137K温度范围内调控合金的居里温度.分子磁矩随有序化占位也有相应变化,分布在2.28μ_B/f.u.—2.48μ_B/f.u.之间.理论计算和实验对比可证明Fe_2CrGa合金是Hg2CuTi型Heusler合金.

The KKR-CPA-LDA method was used to calculate the electronic and the magnetic structures of Fe_2CrGa alloy.The results indicate that Fe_2CrGa alloy prefers to crystallize in Hg_2CuTi-type structure rather than L2_1 one.The analysis of density of states reveals that the intra-atomic exchange splitting affected by crystal field plays an important role in forming the Hg2CuTi-type structure. The molecular magnetic moments measured experimentally are in a range of 2.28—2.48_（μB） / f.u.,which is very close to that expected theoretically by the calculations based on the Hg_2CuTi-type structure,but not based on the L2_1 structure.The experimental results also show that the Curie temperature of Fe_2CrGa alloy can be continuously manipulated from 308K to 445K by heat-treating under the various conditions,indicating a high sensitivity of the exchange interaction to the atomic ordering in this system.