We have studied spin excitations in nanosized magnetic films in the Heisenberg model with magnetic dipole and exchange interactions by the spin operator diagram technique. Dispersion relations of spin waves in thin magnetic films (in two-dimensional magnetic monolayers and in two-layer magnetic films) and the spin-wave resonance spectrum in N-layer structures are found. For thick magnetic films generalized Landau-Lifshitz equations are derived from first principles. Landau-Lifshitz equations have the integral (pseudodifferential) form, but not differential one. Spin excitations are determined by simultaneous solution of the Landau-Lifshitz equations and the equation for the magnetostatic potential. For normal magnetized ferromagnetic films the spin wave damping has been calculated in the one-loop approximation for a diagram expansion of the Green functions at low temperature. In thick magnetic films the magnetic dipole interaction makes a major contribution to the relaxation of long-wavelength spin waves. Thin films have a region of low relaxation of long-wavelength spin waves. In thin magnetic films four-spin-wave processes take place and the exchange interaction makes a major contribution to the damping. It is found that the damping of spin waves propagating in magnetic monolayer is proportional to the quadratic dependence on the temperature and is very low for spin waves with small wavevectors. Spin-wave devices on the base of nanosized magnetic films are proposed -- tunable narrow-band spin-wave filters with high quality at the microwave frequency range and field-effect transistor (FET) structures contained nanosized magnetic films under the gate electrode. Spin-wave resonances in nanosized magnetic films can be used to construct FET structures operating in Gigahertz and Terahertz frequency bands.
Substrate induced magnetic anisotropies and magneto-optical response in YIG nanosized epitaxial films on NdGG(111)
用激光分子束外延方法在Nd 3Ga 5 O 12衬底上生长了Y3 Fe 5 O 12纳米外延薄膜。磁光极性克尔效应、铁磁共振和自旋波传播测量表明，与YIG/GGG系统相比，与应力相关的各向异性场具有相反的符号。这导致了有效磁化强度的显著降低，这为获得具有垂直磁化强度的YIG薄膜以利用前向体自旋波开辟了前景。纵向磁光克尔效应磁强计揭示了一个大的贡献二次磁化条款到介电常数张量在光学频率。这种效果强烈增加，随着温度的降低，并解释了交换耦合到Fe 3+离子的界面Nd 3+离子的磁化。
Influence of magnetic disorders on Quantum Anomalous Hall Effect in Magnetic Topological Insulator Films beyond the two-dimensional limit
在磁性掺杂（Bi，Sb）2 Te 3上制备的磁性拓扑绝缘体（MTI）薄膜中，实验上实现了量子反常霍尔效应（QAHE）。在具有沿法线方向（z方向）的易磁化轴的MTI薄膜中，磁性掺杂剂的取向围绕易磁化轴随机分布，充当磁性紊乱。借助于非平衡格林函数和Landauer-Buttiker形式，我们数值研究了磁无序对MTI薄膜QAHE的影响.研究发现，由于无带隙侧表面态的存在，只要所有磁性掺杂剂的磁矩的z分量为正，QAHE即使在磁无序的情况下也能得到保护.更重要的是，这种磁无序还抑制了手性边缘态的耗散，提高了MTI薄膜中QAHE的质量。此外，磁无序的影响很大程度上取决于薄膜的厚度，并在一定的厚度达到最佳的影响。这些发现是QAHE在三维系统中的新特征，而不是在二维系统中。
Magnetic properties of ferromagnetic Gd$_5$Si$_4$-Fe$_3$O$_4$ bilayer thin film heterostructure
薄膜的磁性不同于相应的块体材料，并且由于其尺寸和维度的减小而显示出新颖的物理特性。不同材料的薄膜界面之间的交换偏置也会导致磁特性的深刻变化。本文采用高真空射频磁控溅射法在硅衬底上制备了不同厚度的Fe $_3$ O $_4$、Gd $_5$ Si $_4$和Fe $_3$ O $_4$ -Gd $_5$ Si $_4$双层薄膜。它们的磁化强度在室温下在3 T的磁场和50 K至400 K的温度之间进行了测量。Gd 5Si 4薄膜由于暴露于空气中而导致氧化。所有样品的沉积膜厚度均大于50 nm，表现出铁磁性。
