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1.
The exact magnetization pattern of magnetic films close to a spin-reorientation transition is difficult to analyze due to the intrinsically three-dimensional (3d) variation of the orientation of the local magnetization. We present a technique how this can be performed, based on the analysis of high quality 2d polarization maps from a single scanning electron microscope with polarization analysis (SEMPA) measurement with tilted sample. The key tool is the statistical distribution of all occurring polarization doublets, visualized in a 2d histogram plot. From the shape of the distribution the type of transition—canted-phase, or coexisting phases—can be inferred. For the canted-phase state, the canting angle can be accurately determined from geometrical considerations. With help of the histogram the image data can be analyzed and the three components of the magnetization can be calculated for most points of the image. For a Co/Pt multilayer film we found a cone state. The magnetization forms a complex pattern consisting of out-of-plane domains while the in-plane magnetization shows a maze pattern. 相似文献
2.
Molecular-dynamics computer-simulation of an ionic molecular solid LiKSO4 has been carried out at 300 and 1000 K using the atom-atom potentials obtained from lattice dynamical studies. We observe
hopping of lithium ions to interstitial positions which is related to reorientations of sulphate tetrahedra. 相似文献
3.
水力裂缝转向作为压裂过程中的一种重要现象,可造成近井筒裂缝的弯曲,对于裂缝中支撑剂的传输和流体的流动规律具有很大影响,可最终影响水力压裂的成败和人工裂缝的导流能力。统计了长庆油田水平井压裂施工的部分资料,分析了长庆油田水平井压裂的特点。结合二维裂缝的平面应变模型,建立了裂缝转向的曲率半径与地层物性参数和压裂施工参数的关系,并针对性地分析了不同参数对于裂缝曲率半径的影响。结果表明,水平应力差对裂缝的转向距离有决定性的影响,压裂施工排量对水力裂缝高度的增长贡献显著,控制排量、延长注液时间能有效增加裂缝长度。结论对于压裂参数优化设计和水力压裂施工具有参考意义。 相似文献
4.
Studies of spatial representation generally focus on flat environments and visual input. However, the world is not flat, and slopes are part of most natural environments. In a series of 4 experiments, we examined whether humans can use a slope as a source of allocentric, directional information for reorientation. A target was hidden in a corner of a square, featureless enclosure tilted at a 5° angle. Finding it required using the vestibular, kinesthetic, and visual cues associated with the slope gradient. In Experiment 1, the overall sample performed above chance, showing that slope is sufficient for reorientation in a real environment. However, a sex difference emerged; men outperformed women by 1.4 SDs because they were more likely to use a slope-based strategy. In Experiment 2, attention was drawn to the slope, and participants were prompted to rely on it to solve the task; however, men still outperformed women, indicating a greater ability to use slope. In Experiment 3, we excluded the possibility that women's disadvantage was due to wearing heeled footwear. In Experiment 4, women required more time than men to identify the uphill direction of the slope gradient; this suggests that, in a bottom-up fashion, a perceptual or attentional difficulty underlies women's disadvantage in the ability to use slope and their decreased reliance on this cue. Overall, a bi-coordinate representation was used to find the goal: The target was encoded primarily with respect to the vertical axis and secondarily with respect to the orthogonal axis of the slope. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
5.
In our previous paper, we investigated the influence of the phase structure on the polymeric chain diffusion in the complexed crystals of solid polymer electrolytes of PEO:LiAsF6 and PEO:LiCF3SO3. We observed that with the increase of the crystallinity, the chain diffusion rate decreases dramatically. In this work, by employing the 13C CODEX NMR spectroscopy, we demonstrate that opposite to the behavior of the chain diffusion motion, the local reorientation motion of polymeric chains within the complexed crystals are greatly increased with the increase of the crystallinity, which is accompanied by the change of the phase structure. The relationship between the different molecular motions within the complexed crystals and the phase structure are discussed therefore. 相似文献
6.
《Ceramics International》2020,46(11):18758-18762
Experiments for heavy rare-earth iron garnets Ho3Fe5O12 and Er3Fe5O12 show a compensation effect characterized by a near zero magnetization at 134 K and 80 K, respectively. The magnetic entropy change calculated according to the Maxwell's relation is shown to be positive and negative, indicating both normal and inverse magnetocaloric effects exist in the sample. The critical temperature (134 K for Ho3Fe5O12, 80 K for Er3Fe5O12) of the two types of magnetocaloric effect occurs at almost the same temperature as the compensation point. However, the compensation effect is attributed to the multiple exchange interactions among the octahedral sites Fe3+, the tetrahedral sites Fe3+ and the dodecahedral sites R3+, while the reversal of the magnetocaloric effect is originated from the spin reorientation. The maximum magnetic entropy change of the normal magnetocaloric effect is 4.72 J kg−1 K−1 for Ho3Fe5O12 at 34 K and 4.94 J kg−1 K−1 for Er3Fe5O12 at 24 K, respectively. Moreover, all the positive slopes of basic Arrott plots suggest only the second-order phase transition existing in Ho3Fe5O12 and Er3Fe5O12. 相似文献
7.
Kevin Heritage Ben Bryant Laura A. Fenner Andrew S. Wills Gabriel Aeppli Yeong‐Ah Soh 《Advanced functional materials》2020,30(36)
First‐order phase transitions, where one phase replaces another by virtue of a simple crossing of free energies, are best known between solids, liquids, and vapors, but they also occur in a wide range of other contexts, including even elemental magnets. The key challenges are to establish whether a phase transition is indeed first order, and then to determine how the new phase emerges because this will determine thermodynamic and electronic properties. Here it is shown that both challenges are met for the spin reorientation transition in the topological metallic ferromagnet Fe3Sn2. The magnetometry and variable temperature magnetic force microscopy experiments reveal that, analogous to the liquid–gas transition in the temperature–pressure plane, this transition is centered on a first‐order line terminating in a critical end point in the field‐temperature plane. The nucleation and growth associated with the transition is directly imaged, indicating that the new phase emerges at the most convoluted magnetic domain walls for the high temperature phase and then moves to self‐organize at the domain centers of the high temperature phase. The dense domain patterns and phase coexistence imply a complex inhomogenous electronic structure, which can yield anomalous contributions to the electrical conductivity. 相似文献
8.
9.
《Intermetallics》2016
We report a correlation between magnetoresistivity Δρmag and magnetic entropy change ΔSmag for specified crystallographic directions of a HoAl2 single crystal. This ferromagnetic compound shows differentiated behavior among the members of the RAl2 series due to the presence of spontaneous spin reorientation. We discussed this effect in order to establish a relationship between the two quantities studied. The calculations were performed using a self-consistent model based on a Hamiltonian containing exchange, Zeeman and crystal field terms. We found that the normalized relation {Δρmag} = (T/TC)m{ΔSmag}, with m = 0.1 for the [100] and [110] directions matches satisfactorily the two quantities. 相似文献
10.
在拉应力为50-200MPa和150-400℃温度循环条件下,研究了应力和温度循环次数对T225合金中氢化物再取向程度的影响.结果表明,随着应力的增大和温度循环次数的增加,T225合金中氢化物再取向的程度提高.氢化物发生再取向时的应力存在一个阈值,当应力低于这个阈值时,即使增加温度循环次数,氢化物再取向也不明显;当应力大于应力阈值时,氢化物应力再取向的程度与应力和温度循环次数的关系式为:Rσ=0.735exp[0.0167N^0.224(σ-σth^N)].应力阈值随着温度循环次数的增加而降低,它们之间的关系为σth^N=101+60exp(-0.2N). 相似文献