Structural and magnetic phase transitions in Mn-Ni alloys
Structural and magnetic phase transitions in Mn-Ni alloys
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DOI：
10.1103/physrevb.61.12159
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发表时间：
2000-05-01
影响因子：
3.7
通讯作者：
Thompson, JR
中科院分区：
文献类型：
--
作者：
Fishman, RS;Lee, WT;Thompson, JR
当Ni含量超过约18%时，预期Mn-Ni合金支持两种不同的非共线自旋密度波（SDW）相。在T-N和T-t之间的fee相中，认为出现了沿晶体对角线沿着具有矩的三电子SDW。在T-t以下，c>a的fct相被认为包含双e SDW，其力矩在ab平面中并且与晶轴成45度角。基于电阻率、中子散射和磁化率的测量，我们发现Mn_（1-x）Ni_x（x = 0.20）合金的结构相变和磁性相变是不同的，在T_（1-x）Ni_x合金中，T_（1-x）Ni_x合金在T_（1-x）Ni_x合金中的结构相变远高于T_（1-x）Ni_x合金在T_（1-x）Ni_x合金中的磁性相变。一个哈密顿量，其中包括弹性，magnetoelastic，和非共线能量被用来描述这两个转变。在T-t和T-m之间的四方相中，我们的模型预测了一个新的SDW相，其力矩从晶体对角线向ab平面倾斜。自旋波谱中的能隙被预测为在Tm处不连续地变化。
When the Ni concentration exceeds about 18%, Mn-Ni alloys were expected to support two different noncollinear spin-density wave (SDW) phases. A triple-e SDW with moments along the crystal diagonals was believed to appear in the fee phase between T-N and T-t. Below T-t, the fct phase with c>a was believed to contain a double-e SDW with moments in the ab plane and at 45 degrees angles from the crystal axes. Based on resistivity, neutron-scattering, and susceptibility measurements, we show that the structural and magnetic phase transitions in a Mn1-xNix alloy with x approximate to 0.20 are actually distinct, with the structural phase transition at T-t approximate to 250 K lying far above the magnetic transition at T(m)approximate to 125 K. A Hamiltonian which includes elastic, mag netoelastic, and noncollinearity energies is used to describe these two transitions. In the tetragonal phase between T-t and T-m, our model predicts a new SDW phase with moments tilted away from the crystal diagonals toward the ab plane. The energy gap in the spin-wave spectrum is predicted to change discontinuously at T-m.