共查询到20条相似文献,搜索用时 15 毫秒
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New photo-magnetic effects with an indefinitely long-time memory are found at room temperature in the epitaxial Mg0.75Mn0.21Co0.04Fe2O4 ferrite film. Illumination of the ferrimagnetic material with low-intensity (0.4 W cm−2) circularly polarized light with or without a static magnetic field in the Faraday effect geometry results in a number of nonlinear effects in both space and time. In a uniform crystal with cubic symmetry, the long-lived photo-induced magnetization (PIM) with a unidirectional anisotropy appears along the direction of the incoming light. The effects depend on a combination of magnetic field H and the helicity of circularly polarized light σ. Two combinations H+,σ+ and H−,σ− lead to a photo-induced unidirectional anisotropy with a shift of the hysteresis loop along an applied field and a change in loop parameters. The loop contracts by a factor of two, the shift of the mid-point Hsh increases by factor of five surpassing the coercivity Hc, the coercivity Hc1 and remanence Mr1 (for decreasing applied field) reverse the sign, increasing by 9 Oe and reducing by a factor of 4.5, respectively. The effects cannot be erased by a conventional demagnetization (using an AC current that is reduced to zero amplitude), but can be removed using an illumination with two other combinations (H+,σ− and H−,σ+) as well as by heating at temperatures higher than the Curie temperature. This long-lived room-temperature memory effect may arise from the formation of complex photo-induced defects including photo-induced magnetic polarons. The possible mechanisms responsible for the appearance of a room-temperature photo-induced unidirectional anisotropy with a long-lived memory are discussed. These new photo-magnetic effects may find an application in magneto-optical memory devices. 相似文献
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R. E. Ershov 《Russian Physics Journal》1970,13(11):1454-1456
In a real ferromagnet there are a large number of domains differing greatly in energy, so that a domain energy distribution can be introduced. The nonvanishing initial permeability and saturation on the magnetization curve allow an analytic expression to be found for this function and thus for the magnetization curve. Taking the domain interaction into account by introducing a starting field allows the B(H) dependence found to be generalized to weak fields. Analysis of ideal magnetization curves shows that the superposition on a constant field of varying fields having nonvanishing amplitudes reduces the starting field to zero, i.e., removes the magnetic interaction. The B, H plane can be thought of as a complex plane, each point of which is associated with some state of the ferromagnet. A transformation is made from the magnetization curve to the remagnetization curve by a linear transformation of this complex point. In this manner, a transformation can be made from the B(H) dependence found for weak fields to an analytic expression for the hysteresis loop in the same field range.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 11, pp. 59–62, November, 1970. 相似文献
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研究了Pb[(Zr052Ti048)095(Mn1/3Nb2/3)005]O3 (PMnN_PZT) 铁电陶瓷电滞回线的温度和频率响应,结果显示在高频和室温条件下测试铁电特性时,电滞回线呈现“束腰”形状,而不是通常所看到的方形回线 . 在低频和高温条件下测试时才能观察到正常的方形回线,同时,诸如矫顽场、极化强度、 内偏场这些重要的铁电参数也会随频率和温度发生显著的变化. 剩余极化强度随频率和温度 的大幅增长表明“束腰” 电滞回线有可能是由于缺陷偶极子引起的. 电滞回线形状与温度 和频率存在较强的相关性说明缺陷偶极子存在一特征弛豫时间,缺陷偶极子反转响应速度由 此弛豫时间决定.
关键词:
电滞回线
氧空位
频率响应
温度响应 相似文献
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Hong-guo ZhangYu-Jie Zhang Weng-Hong Wang Guang-Heng Wu 《Journal of magnetism and magnetic materials》2011,323(15):1980-1984
A series of Co ferrites (CoxFe3−xO4 (x=0−1)) were prepared using solid-state method in this work. The aging effect of their structures and constrictions of hysteresis loops under low magnetic field were investigated. It was found that during the aging process, the migration of trivalent (bivalent) ions between tetrahedral (A-site) and octahedral (B-site) coordination induced a shrinking of the lattice, which would expand again due to the precipitation of Fe3+ after a much longer aging time. The first process caused a pronounced constriction of the loops, due to the uniaxial anisotropy led by this migration. The depression of constriction could attribute to both the expansion of lattice and the change of ionic ratios as a result of the second-phase-precipitation. The impacts of Co content, aging time and temperature upon the constriction were also discussed. 相似文献
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《Physica B: Condensed Matter》2000,275(1-3):5-10
We present numeric simulations of switching processes in small ferromagnetic particles. The dynamics of these processes and the influence of the dynamics of the applied and internal fields on the magnetization reversal are studied. In particular, the derivative in time of the effective fields influences the hysteresis of these particles. It is shown that fast switching, as is required in high-speed data storage, reduces the coercive field. A dynamically corrected Stoner–Wohlfarth dependence of the nucleation field is introduced for the limit of high-field rates and low damping. Implications of these findings are discussed for both, numerical simulation of hysteretic properties and the interpretation of experimental data. 相似文献
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E. Z. Meilikhov R. M. Farzetdinova 《Journal of Experimental and Theoretical Physics》2005,100(6):1112-1120
A simple analytical model is developed to explain the phenomenon of exchange bias of the hysteresis loop in a two-dimensional ferromagnet-antiferromagnet bilayer. A solution of the magnetic relaxation equation is obtained within the framework of the generalized mean field theory, which describes the shape of the hysteresis loop and shows its dependence on the properties of a model interface in the system under consideration. 相似文献
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V. N. Shut 《Physics of the Solid State》2013,55(7):1438-1441
Possible reasons of the difference in polarization characteristics of thin-film and bulk ferroelectrics with a composition gradient have been considered. 相似文献
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Waldmann O Koch R Schromm S Müller P Bernt I Saalfrank RW 《Physical review letters》2002,89(24):246401
At low temperatures, the magnetization of the molecular ferric wheel NaFe6 exhibits a step at a critical field B(c) due to a field-induced level crossing. By means of high-field torque magnetometry we observed a hysteretic behavior at the level crossing with a characteristic butterfly shape which is analyzed in terms of a dissipative two-level model. Several unusual features were found. The nonzero bias field of the level crossing suggests the possibility of cooling by adiabatic magnetization. 相似文献
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近几年的高考题中,出现了不少立意深刻的开放性问题,相对于传统试题,开放性试题具有条件模糊、情景新颖、信息丰富、模型隐蔽、方法灵活、结论不唯一,甚至涉及跨学科综合等特点.因此,同学们感到有一定难度,本文就该类问题解法作如下剖析,供同学们参考。 相似文献
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