磁性斯格明子晶格的磁弹现象与机理

近年来,人们在一些具有手性相互作用的磁性体材料及薄膜中成功观测到具有非平凡拓扑性质的二维自旋结构,称作磁性斯格明子.在大部分情况下,磁性斯格明子自发地聚集成一种晶格结构,称作斯格明子晶格.孤立的斯格明子由于其奇特的拓扑性质以及优异的电流驱动性质等"局域化特征"受到人们的广泛关注.与此相对,斯格明子晶格作为一种新颖的宏观磁性相,可能与材料固有的多场耦合性质发生相互作用进而引发许多奇特的宏观物理现象乃至新性质.在此范畴内,人们发现由于手征磁体内禀的磁弹耦合,斯格明子晶格不但对材料的力学性质产生影响,而且在外力作用下自身具备"层展的弹性性质".本文对相关现象进行梳理,并基于一种针对B20族手征磁体磁弹耦合效应普遍适用的热力学唯象模型,逐一简述对于不同类型的磁弹现象如何建模分析,进而给出其中一部分现象的实验与理论结果比对.最后,对这一领域的发展提出几个可供进一步探索的方向.     

AC-current-induced magnetization switching in amorphous microwires

We studied the influence of AC current flowing through microwires, on magnetization dynamics. We used a previously developed Sixtus-Tonks modified setup to evaluate the domain wall (DW) velocity within the microwire. However, instead of a magnetizing solenoid, we used a current flowing through the microwire. We observed that the AC current flowing through the annealed Co-rich microwire leads to remagnetization by fast domain wall propagation. The estimated DW velocity was approximately 4.5 km/s, which is similar to and even higher than that reported for the magnetic-field-driven domain wall propagation in Fe- and Co-rich microwires. We measured the DW velocity under tensile stress, and found that the DW velocity decreases under applied stress. An observed DW propagation induced by the current flowing through the microwire is explained considering the influence of an Oersted magnetic field on the outer domain shell. This field has a circular easy magnetization direction and magnetostatic interaction between the outer circumferentially magnetized shell and the inner axially magnetized core.     

Dispersion equation of magnetoelastic shear waves in irregular monoclinic layer

This paper studies the propagation of horizontally polarized shear waves in an internal magnetoelastic monoclinic stratum with irregularity in lower interface. The stratum is sandwiched between two magnetoelastic monoclinic semi-infinite media. Dispersion equation is obtained in a closed form. In the absence of magnetic field and irregularity of the medium, the dispersion equation agrees with the equation of classical case in three layered media. The effects of magnetic field and size of irregularity on the phase velocity are depicted by means of graphs.     

Magnetoelastic instability in the XXZ rings with next-nearest neighbour coupling

This paper numerically investigates the magnetoelastic instability in the S = 1/2 {XXZ} rings containing finite spins N with antiferromagnetic nearest-neighbour ({NN}) and next-nearest neighbour ({NNN}) coupling. It finds that, as the {NN} anisotropy Δ₁ equals the {NNN} anisotropy \varDelta₂, there exists a critical {NNN} coupling strength J₂^c(≈0.5), at which the systems always locate in dimerized phase for arbitrary large spring constant. As Δ₁ \ne Δ₂, the values of J₂^{\rm c} are dependent on N and the difference of (Δ₁-\varDelta₂).     

内共振条件下轴向运动梁磁弹性超谐共振研究

以载流导线激发的磁场中轴向运动梁为研究对象,同时考虑外激励力作用,推导出梁的磁弹性非线性振动方程．通过位移函数的设定和伽辽金积分法,将非线性振动方程离散为常微分方程组．采用多尺度法得到系统的近似解析解．应用Matlab 和Mathematica 软件求解幅频响应方程,并对稳态解进行稳定性判定．通过具体算例得到前两阶假设模态的响应幅值随不同参数的变化规律．结果发现：系统在内共振条件下发生超谐波共振时,二阶假设模态幅值明显小于一阶;随着外激励的增大,多值解区域范围明显缩小;随着电流强度增加,振动幅值减小,表明载流导线能够起到控制共振的作用．     

Spatial shapes of magnetoelastic shear body waves at the transmission edges in a periodically inhomogeneous magnetostrictive medium

The spatial shapes of magnetoelastic shear body waves at the transmission edges in a periodically inhomogeneous magnetostrictive medium are studied. Numerical results are obtained for a two-component composition of ferrite and nonmagnetic dielectric __________ Translated from Prikladnaya Mekhanika, Vol. 42, No. 3, pp. 61–69, March 2006.     

电磁场中变厚度载流圆板的非线问题

本文建立了在非定常电磁场和机械场作用下变厚度载流弹性圆板在非线性变形状态下的磁弹性二维关系方程和运动方程，给出了弹性圆板在轴对称条件下的数值解．     

Magnetoelastic shear body waves in periodically inhomodeneous media

The shapes of magnetoelastic shear body waves in periodically inhomogeneous magnetostrictive dielectric media are studied with emphasis on wave shapes in the neighborhood of the zones of interaction of elastic and magnetostatic waves __________ Translated from Prikladnaya Mekhanika, Vol. 42, No. 10, pp. 13–20, October 2006.     

The anomalies of the longitudinal magnetothermoelectric power of metal in the vicinity of electronic topological transition

Summary The longitudinal magnetothermoelectric power (MTEP) is calculated for metal in magnetic field and in the vicinity of electronic topological transition (ETT). The giant oscillations of MTEP as a function of applied magnetic field are found. These oscillations originate from the energy dependence of electron relaxation time in magnetic field and they are peculiar to any normal metal independently of the shape of its Fermi surface. Nevertheless the ETT essentially changes the form and magnitude of such oscillations. The results of recent experimental investigation of MTEP in cadmium monocrystals under the pressure and in magnetic field are discussed from the point of view of the presented theory.

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Riassunto Si calcola la potenza magnetotermoelettrica longitudinale per metalli nel campo magnetico e in vicinanza della transizione topologica elettronica (ETT). Si trovano oscillazioni giganti di MTEP in funzione del campo magnetico applicato. Queste oscillazioni originano dalla dipendenza dall'energia del tempo di rilassamento dell'elettrone nel campo magnetico e sono peculiari di ogni metallo normale indipendentemente dalla forma della sua superficie di Fermi. Cionondimeno ETT cambia essenzialmente la forma e la grandezza di tali oscillazioni. Si discutono i risultati di una recente ricerca sperimentale di MTEP in monocristalli di cadmio sotto pressione e nel campo magnetico dal punto di vista della teoria presentata.

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Резюме Вычисляется продольный коэффициент магнитнотермоэлектродвижущей силы для металла в магнитном поле и вблизи электронного топологигеского перехода. Обнаружены заметные осцилляции коэффициента магнитнотермоэлектродвижущей силы в зависимости от велигины приложенного магнитного поля. Эти осцилляции обусловлены энергетической эависимостью времени релаксации электронов в магнитном поле. Эти осцилляции являются характерными для любого нормального металла, независимо от формы поверхности Ферми. Тем не менее, электронный топологический переход существенно изменяет форму и величину таких осцилляций. В рамках предложенной теории обсуждаются результаты недавних экспериментальных исследований коэффициента магнитнотермоэлектродвижущей силы в монокристаллах кадмия под действием давления и в магнитном поле.