共查询到19条相似文献,搜索用时 255 毫秒
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使用飞秒时间分辨抽运-探测磁光Kerr光谱技术,实验研究了圆偏振光抽运面内磁化FePt和垂直磁化GdFeCo薄膜的磁化演化动力学,发现在时间延迟零点处均出现瞬态Kerr峰.分析了此Kerr峰的起源,指出此瞬态Kerr峰与铁磁性无关,可能起源于自由电子的顺磁磁化,而顺磁磁化的外磁场来自圆偏振抽运光的逆Faraday效应.基于顺磁磁化模型的计算结果支持此观点.基于此观点,逆Faraday效应感应的磁场脉冲宽度应该与激光脉冲宽度一致. 相似文献
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基于相对论夸克模型,在夸克层次上研究了N-Δ的质量和二者的能量劈裂,通过引入了赝标量π介子云效应,得到了π和核子之间的耦合常数gπNN,以及单胶子交换势和单π介子交换势分别对N-Δ能量劈裂的贡献,计算结果较好地与实验值得到了吻合.另外我们还比较了相对论与非相对论夸克模型在处理上的不同. 相似文献
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FePt合金薄膜由于具有较强的磁各向异性而在磁信息和磁光信息存储中具有重要的应用.C掺杂可精确调控薄膜的磁各向异性,从而可有效地改变薄膜的矫顽场.通过超短激光脉冲与铁磁薄膜相互作用,可以获得非平衡状态下电子、自旋和晶格等自由度之间的动态耦合参数,这是研究超快磁记录材料的物理基础.本文基于瞬态磁光Kerr效应,研究了两种C掺杂浓度下FePt薄膜的超快磁光响应.实验结果表明:瞬态Kerr信号与外加磁场正相关,磁场反向,Kerr信号反号,而瞬态反射率与外加磁场无关;不同C掺杂的FePt薄膜的矫顽场不同,软磁的退磁时间显著小于硬磁薄膜的退磁时间.我们还观测到超快激光在铁磁薄膜中诱导频率约为49 GHz的相干声学声子,该声子的频率与外加磁场无关.实验结果为设计和研制新型磁光薄膜提供了实验依据. 相似文献
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为了进一步研究在疲劳载荷下含铜4%的铝合金中的位错钉扎过程,进行了经过不同时效的试样的扭转疲劳试验,测定了经过各种应力循环数N以后的滞后迴线的形状和面积,从而算出了在每次循环中的能量消耗ΔE和最大抗扭矩Tm。所选择的时效温度和时效时间是使试样中分别有G.P.[1]区,G.P.[2]区,θ′相和稳定的θ相出现。把所得的ΔE-N曲线和Tm-N曲线的变化情况作比较时可以看出,在疲劳载荷的起始阶段引起位错钉扎的并不是由于相变产物如G.P.[1]或[2]区的作用。比较并分析了在各种时效状态下的第一周能量消耗值(ΔE)1的变化,结果指出,在所研究的铝铜合金的情形,产生ΔE的原因是由于在位错附近的点阵中有起伏的内应力场出现,因为位错在这种内应力场中往复运动需要作功。产生这种起伏的应力场的因素有点缺陷(空位和溶质原子)、原子簇、G.P.[1]区和G.P.[2]区,或者其他种不在位错线上聚集或成核的缺陷。根据上述分析,可以认为,在疲劳载荷中,使位错钉扎的是由于溶质原子气团的形成。溶质原子在疲劳过程中通过空位的帮助进入位错,形成气团,使位错被钉扎。被钉扎的位错的动性减低,因而ΔE下降。在时效过程中,在位错线上成核的θ′和θ相,对于位错线也起着一定的钉扎作用。由上述的图象还可以推知,G.P.[1]区和G.P.[2]区不是在位错线上成核的,而θ′相和θ相则是在位错线上成核的。 相似文献
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克尔磁光效应的经典理论分析 总被引:1,自引:0,他引:1
本文引入与自旋-轨道相互作用等有关的有效场概念,运用经典电磁场理论,推导了磁光克尔旋转的明确表达式.证明了各种磁光介质的极向克尔旋转θ_k的实部θ′_k和虚部θ″_k均与有效场H_i成正比,在铁磁性介质中近似与vM成正比,M为磁化强度,在亚铁磁性等介质中近似与(?)v_iM_i成正比,M_i为i次点阵的磁化强度.同时还证明了近似的横向克尔旋转θ_k~t与H_i~2正比;θ_k和θ_k~t的温度特性取决于H_i的温度特性. 相似文献
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固体材料的磁光效应及其应力、温度和色散特性 总被引:2,自引:1,他引:1
本文应用经典电磁场理论推导了磁光效应的基本关系式,运用有效场概念得到了适用于各种磁光介质情形的法拉第旋转θ的明确表达式.证明了θ与有效场H_(?)成正比关系并具有强的色散特性;在弱磁介质中外应力对θ具有明显的影响;逆磁性介质的费尔德常数V与温度T无关,有些顺磁性介质的费尔德常数V_p与磁化率x的比值V_p/X=G(1+RT);在反铁磁性和亚铁磁性介质中,θ与各次点阵磁化强度M_(?)有关,其温度特性不仅取决于次点阵磁化强度,而且取决于磁光系数与温度的依赖关系.计算结果与实验符合得很好.计算还表明,当光的传播方向与H_(?)方向垂直时,入射到磁光介质中的线偏振光会分解成一个椭圆偏振光和一个线偏振光,这种磁双折射的相位延迟率的实部和虚部均与H_(?)~2成正比. 相似文献
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基于磁性金属颗粒膜Kerr磁光效应的关系,结合电子跃迁和自由电子共振模型及实验数据,分析了金属颗粒膜的磁光Kerr旋转和Kerr椭偏现象,由分析研究表明:在磁性金属颗粒材料中Kerr旋转和Kerr椭偏率光谱(Kerr效应)中的共振峰不是由单一电子的跃迁引起,其中由于等离子体激化元的存在,而引起的等离子体共振行为在此产生了相当的影响. 亦即对磁光Kerr旋转和Kerr椭偏率起作用的是电子跃迁与自由电荷载流子的等离子共振相互作用共同引起的. 这一结论与对较大Kerr效应的4f 化合物的相关实验强烈的Kerr效应和明显的共振结构相一致,这在铥原子化合物(TmS,TmSe)和铈化合物(CeSb,CeSb0.75Te0.25,CeTe.)及L10FePt膜中都已观察到这一现象. 相似文献
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用磁控溅射法制备了Pt/Co/Pt/Ni系列样品,其中Ni层具有不同的厚度.通过测量样品的Kerr转角、椭偏率、折射率和吸收率,推算出了四个等效电导张量元σ1xx,σ2xx,σ1xy,σ2xy随Ni层厚度的变化情况.再结合电导张量元与Kerr角的理论公式,分析了在Ni层厚度的变化过程中,每一个电导张量元对Kerr角的贡献;发现在短波段σ2xy起主导作用,而在长波段四个电导张量元共同起作用.经分析认为这是由于在Ni层的增厚过程中,Pt 5d带劈裂程度逐渐减小.与纯Pt/Co膜相比,在Ni层的厚度为0.10—0.23nm的范围内样品具有较低的居里温度和较高的Kerr角,这说明Pt/Co/Pt/Ni多层膜具有较高的应用价值.
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The three main corrections to the binding energy of nuclear matter that involve the Δ (1236) are calculated with exchange effects and realistic correlation functions. It is found that their net effect at KF = 1.36 fm?1 is small, but that their KF dependence has a considerable effect on the saturation density. 相似文献
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V. G. Kravets 《Optics and Spectroscopy》2003,95(1):142-147
The analysis of ultrahigh-density recording in magneto-optical media formed with the use of granular CoAg(Au) films is performed. Due to excitation of plasma oscillations of electrons in granular CoAg(Au) films, the latter make it possible to perform additional focusing of recording radiation and to significantly decrease the size of memory cells. It is suggested that two-layer film CoAg(Au)/TbFeCo/substrate systems be used as recording media for magneto-optical recording. It is shown theoretically that the angle of the Kerr rotation of the plane of polarization θK upon magnetization of such a two-layer structure increases significantly in the range of incident-photon energy from 2 to 4 eV in comparison with the case of TbFeCo magnetic film. Some specific features were detected experimentally in the spectra of θK in the region of excitation of plasma oscillations in nanogranular CoAu and CoAg films at ? ω P ≈ 2.5 and 3.5 eV, respectively, as well as in two-layer CoAg(Au)/TbFeCo film systems. 相似文献
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G. Fishman 《Solid State Communications》1978,27(11):1097-1100
We present a model which describes excitonic polariton effect for direct gap semiconductors where the valence band is degenerate, so that two (“light” and “heavy”) exciton dispersion curves exist and give rise to three polariton branches. It is shown that the quantity is an important parameter in this case, Δ and ELT being respectively the exchange energy and the longitudinal transverse splitting. A comparison with the available data, extracted from Resonant Brillouin Scattering in GaAs, is carried out. It is shown that when only the uppermost and lowest polariton branches can be detected, the measured separation Δexp between these two branches is equal to the longitudinal transverse splitting with a good approximation. In the general case the exact relation between Δ, ELT and Δexp is derived. 相似文献
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A.P. Malozemoff W. Fernengel A. Brunsch 《Journal of magnetism and magnetic materials》1979,12(2):201-214
Domain structures in thin sputtered amorphous FeB films are studied by means of the longitudinal Kerr effect. In addition to the irregular domain structure characteristic of soft magnetic materials, we observe in certain regions a fine equilibrium domain structure with periodicity of a few micrometers. The Kerr contrast indicates that the magnetization at the surface of the film lies partially along the stripe direction. These characteristics and the behavior in applied fields suggests that the domains are similar to type II “strong stripe domains” observed earlier in permalloy films. Extending an earlier theory by Hara, we use a stray-field-free model with tilted orthorhombic anisotropy to show that there are at least two qualitatively different strong stripe structures: type IIa with surface magnetization perpendicular to the stripes and type IIb with surface magnetization at least partially parallel to the stripes. Type IIb is favored when Kp/K0<cos 2θ 0 where K0 is the anisotropy component with axis tilted by θ0 out of the film plane, and Kp is an in-plane anisotropy perpendicular to K0. Strong stripes in amorphous FeB appear to be type IIb while those in permalloy are usually type IIa. 相似文献
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Magnetoreflectance measurements on the ground state of the Γ6 – Γ8 free exciton in cubic ZnSe in magnetic fields up to 18 T are reported. The splitting between the |1, ±1〉 states was derived from the measured difference spectrum between σ+ and σ--polarized reflectance in Faraday configuration. The splitting between the two states corresponding to |2, 0〉 and |1, 0〉 at B = 0 was determined by means of a lineshape analysis. We derive an electron g-factor g = 1.48 ± 0.25, in reasonable agreement with existing k · p calculations, and obtain an effective hole g-value . In addition, we find an upper limit for the short range electron-hole spin exchange energy Δ ? 0.1 meV, which is considerably smaller than values, which is considerably smaller than values reported in the literature, but agrees with recent results on ZnTe obtained by uniaxial stress and also magnetoreflectance measurements. 相似文献