Semiclassical Magnetization Dynamics and Electron Paramagnetic Resonance in Presence of Magnetic Fluctuations in Strongly Correlated Systems

IF 1.1 4区 物理与天体物理 Q4 PHYSICS, ATOMIC, MOLECULAR & CHEMICAL
S. V. Demishev
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Abstract

Semiclassical magnetization dynamics in presence of magnetic fluctuations (including the quantum ones) is derived for a strongly correlated electronic system in the region of the linear magnetic response. Landau–Lifshitz (LL) and Gilbert (G) type equations are obtained with the effective parameters depending on the type of magnetic fluctuations and their magnitude and applied to evaluation of electron paramagnetic resonance (EPR) problem in Faraday geometry. It is shown that in the studied systems LL and G equations may not be equivalent except the case of weak relaxation, where consistent Landau–Lifshitz–Gilbert (CLLG) equation may be considered. Whereas G equation is affected by quantum fluctuations solely, the LL and CLLG equations may be renormalized by magnetic fluctuations of any nature. In contrast to G equation, the LL and CLLG magnetization dynamics may be characterized by the anisotropic relaxation term caused by anisotropic magnetic fluctuations. A consequence of anisotropic relaxation is the unusual polarization effect consisting in strong dependence of the EPR line magnitude on orientation of vector h of the oscillating magnetic field with respect to the crystal structure, so that EPR may be suppressed for some directions of h. In the case of dominating quantum fluctuations, the LL and CLLG equations may lead to a universal relation between fluctuation induced contributions to the EPR line width ΔW and g-factor Δg in the form \(\Delta W/\Delta g = a_{0} k_{B} T/\mu_{B}\), where a0 is a numerical coefficient of the order of unity and independent of the quantum fluctuation magnitude. The applicability of the proposed semiclassical magnetization dynamics models to the EPR in spin nematic phases and detection by EPR method of a new group of magnetic phenomena – spin fluctuation transitions is discussed.

强相关系统中存在磁波动时的半经典磁化动力学和电子顺磁共振
摘要 针对线性磁响应区域内的强相关电子系统,推导了存在磁波动(包括量子波动)时的半经典磁化动力学。根据磁波动的类型及其大小获得了有效参数的 Landau-Lifshitz (LL) 和 Gilbert (G) 型方程,并将其应用于法拉第几何中电子顺磁共振 (EPR) 问题的评估。结果表明,在所研究的系统中,LL 和 G 型方程可能并不等价,除非在弱弛豫的情况下,可以考虑一致的 Landau-Lifshitz-Gilbert (CLLG) 方程。G 方程只受量子波动的影响,而 LL 和 CLLG 方程则可能受到任何性质的磁波动的重正化。与 G 方程相反,LL 和 CLLG 磁化动力学的特点是各向异性磁波动引起的各向异性弛豫项。各向异性弛豫的一个后果是不寻常的极化效应,包括 EPR 线的大小与振荡磁场相对于晶体结构的矢量 h 方向的强烈依赖性,因此在某些 h 方向上 EPR 可能会被抑制。在量子波动占主导地位的情况下,LL 和 CLLG 方程可能会导致波动对 EPR 线宽 ΔW 和 g 因子 Δg 的贡献之间的普遍关系,其形式为 \(\Delta W/\Delta g = a_{0} k_{B} T/\mu_{B}\) ,其中 a0 是一个数量级为一的数值系数,与量子波动大小无关。本文讨论了所提出的半经典磁化动力学模型在自旋向列相 EPR 中的适用性,以及通过 EPR 方法检测一组新的磁现象--自旋波动跃迁。
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来源期刊
Applied Magnetic Resonance
Applied Magnetic Resonance 物理-光谱学
CiteScore
1.90
自引率
10.00%
发文量
59
审稿时长
2.3 months
期刊介绍: Applied Magnetic Resonance provides an international forum for the application of magnetic resonance in physics, chemistry, biology, medicine, geochemistry, ecology, engineering, and related fields. The contents include articles with a strong emphasis on new applications, and on new experimental methods. Additional features include book reviews and Letters to the Editor.
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