Origin of Anisotropy in Gadolinium Crystal Using a New Spin Hamiltonian

• 来源期刊: 中国物理快报（英文版）
• 年，卷（期）: 2020,（5）
• 页码范围: 90-92
• 页数: 3页
• 语种: 英文
• DOI: 10.1088/0256-307X/37/5/057501

摘要

Single crystal rare-earth magnets,such as hexagonal-close-packed gadolinium,usually have a large second order anisotropy K2 and a negative first order anisotropy K1 at low temperatures,which are difficult to explain using microscopic theories.An atomic scale effective spin Hamiltonian F[{Si}]is proposed,which,apart from the usual isotropic nearest neighbor coupling J,consists of two new terms that are different for in-plane and out-of-plane neighbors and which are characterized by two new couplings C1 and C2,respectively.The hybrid Monte-Carlo method is utilized to sample this system to the desired Boltzmann-like distribution exp(-F/kBT).It is found that K2 and K1 are compatible with the experimental values and arise naturally from the exchange anisotropy C1 and C2,which are less than 0.01％ in magnitude of the isotropic exchange energy J.This new model spin Hamiltonian can also be applied to study other magnetic properties.