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本文研究了Sm2(FeNiCoM)17合金(M为非磁性组元)的磁性。样品由六角结构无序型的2∶17主相及少量FeNi合金杂相组成。在六角结构的e轴方向(易磁化方向)观察到下述异常现象:低温(273K以下)时的磁化及反磁化曲线发生明显的跃变,跃变时相应的磁场Hr随温度下降而增大;磁滞迴线是蜂腰型的,温度愈低蜂腰愈明显;升温时磁化强度随温度变化(1.5K至居里点TC)的曲线上出现极大值,其相应的温度Tt随磁场增大而降低;降温时观察到了热磁滞后现象。但在基面(难磁化方向)上及Co含量增多(>18at%)时,样品却表现了正常的铁磁行为。本文提出用磁矩非共线结构排列的自旋再取向相变来解释上述异常现象,并给出自旋倒向所需越过的能垒高度U=9.2×10-15erg,用设想磁结构的模型得到的磁化强度的计算值与实验值也符合得较好。
关键词: 相似文献
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本文利用Goldman-Shen脉冲序列测量了CaSO4·(1/2) H2O样品中结晶水与吸附水1H的交叉弛豫时间为55.1ms。在实验中,发现剩余窄线的磁化矢量随时间的衰减有三个过程。本文对此现象作了一些分析讨论。 相似文献
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当x<0.5时,Nd2(Fe1-xMnx)14B可形成四方晶体结构,空间群为P42/mnm。在低温下,该赝三元化合物的大块铸态样品具有高矫顽力。此矫顽力不依赖于热处理等工艺过程,因此具有内禀性质。内禀矫顽力 iHc与样品的成分有关。Nd2(Fe1-xMnx)14B的起始磁化曲线具有传播场Hp,并且Hp的数值与 iHc接近。这表明内禀矫顽力是由畴壁钉扎造成的。研究了 iHc与温度的变化关系,并估算了钉扎位垒的强度。测量了Nd2(Fe1-xMnx)14B的居里温度和饱和磁化强度。在此赝三元化合物中,交换作用随Mn对Fe的替换而急剧降低。这使得畴壁厚度变窄。Nd2(Fe1-xMnx)14B的磁化和反磁化行为可用窄畴壁的特征来解释。
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在线性增加磁场的条件下,用变频倒扭摆测量了配比成份为(Bi0.8Pb0.2)SrCaCu2Oy的试样在超导态时磁化过程中的低频内耗。测量温度为95K,试样处于零电阻状态,所用频率为0.5-5Hz.在内耗-场强H曲线上观测到内耗峰,它有如下特点:1)峰高随加场速率H的增大而增大,但随测量频率的增大而降低;2)峰值处的场强为4-6mT;3)当H由非零值突然改变至零时,磁化过程特征内耗消失;4)试样处于正常态时,上述特征内耗消失。认为超导体在磁化过程中的上述特征内耗是量子磁通的运动所引起来的。
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本文主要介绍"荧光-1"实验装置物理参数设计, 并依据半经验公式预估在实验装置上可能达到的磁化等离子体状态参数. 理论设计结果表明: "荧光-1"实验装置最大放电电流1.5 MA, 四分之一周期3 μs, 最大反向磁场4 T; 以此为实验平台, 当θ箍缩线圈内充气压力50 mTorr(D2气体)时, 形成的等离子体靶直径约为2 cm, 长度17 cm; 等离子体靶密度6.6×1016 cm-3, 温度 (Ti+Te) 约300 eV; 等离子体平均β值为0.95. 该状态参数接近磁化靶聚变所要求的等离子体靶初始状态参数.
关键词:
脉冲功率技术
反场构形
磁化等离子体
磁化靶聚变 相似文献
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本文根据(1)在偏振锥光下,用显微镜观察到α-LiIO3单晶中层状缺陷在静电场作用下的变化;(2)静电场对a-LiIO3单晶的X射线形貌象的影响;(3)用X射线双晶衍射测得α-LiIO3单晶晶格参数的不均匀性,指出α-LiIO3单晶在静电场作用下中子衍射增强现象是由于晶体中的空间电荷(载流子、杂质离子和空位)在宏观尺度缺陷处富集,造成晶格参数有一定梯度。我们对通常计算中子布喇格散射截面的玻恩近似,引入消光修正,得到畸变晶格中子衍射强度公式,可以解释文献[4—6]中观察到的各种现象。
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本文应用动力学方法计算了均匀非磁化等离子体的电子二级非线性密度涨落,得到了三波在等离子体中相互作用的三级非线性极化率X(3)和第四波K4=K1-K2+K3,ω4=ω1-ω2+ω3的散射功率,与通常的非相干汤姆逊散射相比,其散射信号要大得多,因此,相干四光子散射可以作为等离子体诊断技术的一个重要方法,本文还指出,文献[4]的结果是本文计算的一个简单情况。
关键词: 相似文献
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The local magnetization in the vicinity of a nonmagnetic impurity in a Heisenberg ferromagnet is calculated for different temperatures below the Curie point. In the low-temperature region the spin-wave approximation is used and calculations are carried out up to first-order perturbation theory. The deviation of the magnetization from the value in a perfect magnet turns out to be proportional to T5/2 for very low temperatures. In the region 0.40 TCC numerical solutions are obtained for a molecular field model, under the assumption that the influence of the impurity has a finite range. Extrapolations of both sets of results fit reasonably well together for the nearest and next nearest neighbours of the impurity. 相似文献
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The magnetic field-induced entropy change in a ferromagnet undergoing a second-order phase transition at the Curie point is maximum near that point. The maximum magnetic entropy change, (-ΔS)max, is demonstrated to contain, besides the usual term in H2/3, a small negative term independent of H. Spatial inhomogeneity of real ferromagnetic materials is shown to be the origin of the off-set term, whose magnitude proves proportional to the width of the distribution of local Curie points. 相似文献
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K2CuF4 is a quasi-bidimensional ferromagnet with an easy magnetization plane. The Curie temperature is 6.25 K. We have measured the spin-wave spectrum from 2 to 14 K, and found an exchange integral of 11.4 K between the first neighbours in the basal plane. No measurable dispersion was found along the axis perpendicular to that plane. We have observed a shift in the energy of the magnons, and a broadening of the magnon peak both of which behave differently below and above the Curie temperature. 相似文献
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S. V. Trukhanov A. V. Trukhanov A. N. Vasil’ev A. Maignan H. Szymczak 《JETP Letters》2007,85(10):507-512
For La 0.825 3+ Sr 0.175 2 +Mn3+O 2.912 2? anion-deficient manganite, the specific magnetization, the dynamic magnetic susceptibility, and the heat capacity are investigated. This material is found to be an inhomogeneous ferromagnet below the Curie point T C ≈ 122 K, which is much lower than the Curie point determined for the stoichiometric composition (T C ≈ 268 K). An increase in magnetic field by two orders of magnitude leads to an increase in the Curie temperature by ΔT ≈ 12 K. The presence of oxygen vacancies leads to the frustration of a part, namely, V fr ≈ 22%, of the indirect Mn3+-O-Mn3+ exchange interactions, but the spin glass state is not realized. The ferromagnetic matrix of the material under study is characterized by a scatter in the exchange interaction intensities. The heat capacity is found to exhibit an anomalous behavior. Based on the Banerjee magnetic criterion, it is established that the ferromagnet-paramagnet transition observed for La 0.825 3+ Sr 0.175 2+ Mn3+O 2.912 2? anion-deficient manganite is a second-order thermodynamic phase transition. The mechanism and origin of the critical behavior of the system under investigation are discussed. 相似文献
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J. G. M. Armitage R. G. Graham P. C. Riedi H. Figiel S. F. J. Cox C. A. Scott J. S. Abell K. Yoshimura 《Hyperfine Interactions》1991,64(1-4):395-399
All previous experiments have suggested that Y(Co1−x
Al
x
)2 is a weak itinerant ferromagnet for 0.12<x<0.20. The muon transverse damping rate (λ) increases rapidly near the Curie point forx≥0.155 and for one sample withx=0.145. The value of λ increases with decreasing temperature for other samples withx<0.155 but shows no feature at the Curie point. 相似文献
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M. Gogołwicz J. Warczewski T. Mydlarz I. Okońska-Kozłowska 《Journal of magnetism and magnetic materials》1985,50(1):49-52
For the polycrystalline samples of Mn1?xCuxCr2S4 (x = 0.85, 0.90, 0.95) the magnetization was measured in the temperature range between 77 K and the Curie temperature, TC, using a magnetic balance (Faraday's method) and pulsed magnetic fields up to 2.0 T. The magnetic susceptibility was measured between TC and about 600 K. The Curie temperatures were obtained using the kink point method.In the temperature range between 4.2 and 77 K the magnetization was measured in stationary magnetic fields up to 14 T. The data indicate a noncollinear ferrimagnetic structure. The compounds under investigation can be treated as CuCr2S4 slightly doped with Mn, with a valence distribution Mn2+1?xCu1+xCr3+2?xCr4+xS2?4. 相似文献
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Abstract Y(Co1-xAlx)2 is a weak itinerant ferromagnet for 0.12 < x < 0.20 with a maximum Curie point of about 25 K near x = 0.15. The pressure dependence of the Curie point for samples with 0.14 < x < 0.18 was measured in the temperature and pressure range 5–25 K and 0–8 kbar using a liquid filled lock cell. It was found that Tc was linear in pressure and extrapolated to OK at Pc = 9 ± 1 kbar for all samples. The volume expansion from YCo2 to x = 0.15 is equivalent to a chemical pressure of -40 kbar so ferromagnetism cannot occur at the lattice constant of YCo2. 相似文献
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W. Wasilewski 《Physics letters. A》1982,87(5):253-255
The equations of motion describing relaxation of magnetization fluctuations in the paramagnetic state for a uniaxial ferromagnet have been solved. In the Landau-Ginzburg functional the demagnetization energy has been taken into account. The finite dimensions of a sample have been considered. It has been shown, that a phase transition is generated by fluctuations containing information about the period of the domain structure at the phase transition point Tc1. The obtained formulae describe Tc1 and the period of the domain structure. The results can be used both for bulk materials and thin films. 相似文献
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Approaching the Curie temperature of the cubic ferromagnet CdCr2Se4 from above, the g-factor increasingly shifts from the value predicted by Kittel's formula. In the exchange critical region (susceptibility χ ?1) the g-shift is consistent with δg/g ≈ χ2 following from the complex self-energy. 相似文献