Ames Laboratory, Department of Physics and Astronomy, Iowa State University, 50011, USA.
Phys Rev Lett. 2012 Aug 17;109(7):077201. doi: 10.1103/PhysRevLett.109.077201. Epub 2012 Aug 16.
Predictions of the anisotropic magnetic susceptibility χ below the antiferromagnetic (AFM) ordering temperatures T(N) of local moment Heisenberg AFMs have been made previously using molecular field theory (MFT) but are very limited in their applicability. Here a MFT calculation of χ(T ≤ T(N)) is presented for a wide variety of collinear and noncollinear Heisenberg AFMs containing identical crystallographically equivalent spins without recourse to magnetic sublattices. The results are expressed in terms of directly measurable experimental parameters and are fitted with no adjustable parameters to experimental χ(T ≤ T(N)) data from the literature for several collinear and noncollinear AFMs. The influence of spin correlations and fluctuations beyond MFT is quantified by the deviation of the theory from the data. The origin of the universal χ(T ≤ T(N)) observed for triangular lattice AFMs exhibiting coplanar noncollinear 120° AFM ordering is clarified.
先前使用分子场理论 (MFT) 对各向异性磁 susceptibility χ 在局部磁矩反铁磁 (AFM) 有序温度 T(N) 以下的情况进行了预测，但适用性非常有限。此处，针对包含相同晶体学等效自旋但不依赖于磁子晶格的各种共线和非共线海森堡 AFM，提出了一种对 χ(T ≤ T(N)) 的 MFT 计算。结果以直接可测量的实验参数表示，并通过没有可调参数拟合到文献中来自几个共线和非共线 AFM 的 χ(T ≤ T(N)) 实验数据。理论与数据的偏差量化了超出 MFT 的自旋相关性和涨落的影响。阐明了具有共面非共线 120° AFM 有序的三角晶格 AFM 中观察到的普遍 χ(T ≤ T(N)) 的起源。
