正铁氧体TbFeO $_3$与非Kramers稀土离子的自旋动力学和交换作用
Spin dynamics and exchange interaction in orthoferrite TbFeO$_3$ with non-Kramers rare-earth ion
摘要：
研究了正交晶系TbFeO $_3$钙钛矿的低温自旋动力学。发现非弹性中子散射（INS）谱包含两个模式，对应于化合物中不同的子晶格。铁子系统在T $_N$ = 632 K时为反铁磁有序，并表现出高能磁振子色散.这个子系统的磁动力学已被描述使用线性自旋波理论和我们的解决方案产生相当大的各向异性之间的面内和面外交换相互作用。这种方法以前用于描述TmFeO $_3$化合物中的磁振子色散。在低于40 meV的区域中，在约17、26和35 meV处建立了对应于Tb $^{3+}$离子的三个非色散晶体电场水平。通过对不同温度下的漫散射的研究，阐明了磁关联长度的行为。Tb $^{3+}$离子子系统的行为已在点电荷模型的框架内进行了数值描述。数值计算结果与实验结果吻合得很好，也与斜方晶系钙钛矿稀土子系统的单离子近似的一般概念吻合得很好。
英文摘要：
The low-temperature spin dynamics of the orthorhombic TbFeO$_3$ perovskite has been studied. It has been found that the inelastic neutron scattering (INS) spectrum contains two modes corresponding to different sublattices in the compound. The iron subsystem orders antiferromagnetically at T$_N$ = 632 K and exhibits the high-energy magnon dispersion. Magnetic dynamics of this subsystem has been described using the linear spin wave theory and our solution yields sizable anisotropy between in-plane and out-of-plane exchange interactions. This approach was previously used to describe the magnon dispersion in the TmFeO$_3$ compound. Three non-dispersive crystal electric field levels corresponding to Tb$^{3+}$ ions have been established in the region below 40 meV at about 17, 26, and 35 meV. Study of diffuse scattering at different temperatures has elucidated the behavior of the magnetic correlation length. The behavior of the Tb$^{3+}$ ion subsystem has been numerically described in the framework of the point charge model. The numerical data agree satisfactorily with the experiment and with the general concept of the single-ion approximation applied to the rare-earth subsystem of orthorhombic perovskites.
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