用铁磁共振方法同时测定单晶外延膜的Ku和K1

本文导出了兼具沿晶面法向感生单轴各向异性(K_u)和立方磁晶各向异性(K₁)的任一晶面沿任一方向的薄膜共振场公式,从而提出了同时测定K_u和K₁的一种方法。以(111)晶面为例,给出了具体方法和实验结果。     

Spectroscopic properties of Fe ions at tetragonal sites—Crystal field effects and microscopic modeling of spin Hamiltonian parameters for Fe (S=2) ions in K2FeF4 and K2ZnF4

Magnetic and spectroscopic properties of the planar antiferromagnet K₂FeF₄ are determined by the Fe²⁺ ions at tetragonal sites. The two-dimensional easy-plane anisotropy exhibited by K₂FeF₄ is due to the zero field splitting (ZFS) terms arising from the orbital singlet ground state of Fe²⁺ ions with the spin S=2. To provide insight into the single-ion magnetic anisotropy of K₂FeF₄, the crystal field theory and the microscopic spin Hamiltonian (MSH) approach based on the tensor method is adopted. Survey of available experimental data on the crystal field energy levels and free-ion parameters for Fe²⁺ ions in K₂FeF₄ and related compounds is carried out to provide input for microscopic modeling of the ZFS parameters and the Zeeman electronic ones. The ZFS parameters are expressed in the extended Stevens notation and include contributions up to the fourth-order using as perturbation the spin-orbit and electronic spin-spin couplings within the tetragonal crystal field states of the ground ⁵D multiplet. Modeling of the ZFS parameters and the Zeeman electronic ones is carried out. Variation of these parameters is studied taking into account reasonable ranges of the microscopic ones, i.e. the spin-orbit and spin-spin coupling constants, and the energy level splittings, suitable for Fe²⁺ ions in K₂FeF₄ and Fe²⁺:K₂ZnF₄. Conversions between the ZFS parameters in the extended Stevens notation and the conventional ones are considered to enable comparison with the data of others. Comparative analysis of the MSH formulas derived earlier and our more complete ones indicates the importance of terms omitted earlier as well as the fourth-order ZFS parameters and the spin-spin coupling related contributions. The results may be useful also for Fe²⁺ ions at axial symmetry sites in related systems, i.e. Fe:K₂MnF₄, Rb₂Co_1−xFe_xF₄, Fe²⁺:Rb₂CrCl₄, and Fe²⁺:Rb₂ZnCl₄.     

Optical properties of the red bronze K0.33MoO3

The optical reflectivity of the red bronze K_0.33MoO₃ has been measured on single crystals in the spectral energy range between 0.03 and 12 eV at temperatures from 4 K to 300 K using polarized light. The optical constants have been determined by means of a Kramers-Kronig analysis; the data are interpreted that this compound is a 0.5 eV energy gap semiconductor with very strong anisotropy in the infrared and visible energy range.     

Cubic harmonic analysis of magnetic anisotropy measurements on single crystal HoxTb1−xFe2 laves phase compounds

Room temperature magnetic anisotropy measurements have been made on a series of low anisotropy Ho_xTb_1?xFe₂ compounds, with 0.826 < x < 0.908, using torque magnetometry techniques. An analysis of the data using the conventional expansion of anisotropy energy in terms of the direction cosines proved inadequate because of the presence of higher order contributions to the anisotropy. When these contributions were included in the expansion, non unique anisotropy constants were obtained which were not consistent with the predictions of the single ion model. An analysis of the data using an expansion of the anisotropy in terms of an orthonormal set of functions, namely the cubic harmonics developed by Mueller and Priestly, proved more successful. The results showed that the two lowest order anisotropy constants, κ₄ and κ₆, both varied linearly with holmium concentrations as predicted by the single ion model; however, κ₈, the next higher order term, was not consistent with the predicted behavior. The origin of this contribution is believed to be related to the magnetostriction.     

R2Fe14B(R=Ce,Pr,Gd)磁晶各向异性常数K1,K2随温度的变化

本文在1.5—300K温度范围内测量了R₂Fe₁₄B(R=Ce,Pr,Gd)各向异性常数K₁,K₂和各向异性场H_A随温度的变化。同时用单离子模型计算了Pr³⁺离子对Pr₂Fe₁₄B磁晶各向异性的贡献,得到与实验值半定量符合的结果。 关键词：     

表面弹性项K13对液晶盒临界场强的影响和实验测定

以修正后的Rapini-Papoular公式为基础，得到了有表面弹性能K₁₃存在时，弱锚定向列液晶盒指向矢满足的方程和边界条件。用解析推导和数值计算的方法，详细研究了K₁₃对阈值场强和饱和场强的影响。在理论上给出了检验K₁₃是否存在的一种新方法及用沿面平行校列的弱锚定楔型液晶盒测定K₁₃值的实验方案，并通过数值实验证实了本文所给方法的可行性。     

Magnetic anisotropy of UFe6Al6

A comparative study of magnetization in UFe₆Al₆ and LuFe₆Al₆ single crystals gives clear evidence for the magnetic state of uranium in UFe₆Al₆. Both compounds exhibit the easy-plane type of magnetic anisotropy, however, the anisotropy energy in UFe₆Al₆, characterized by the anisotropy constants K₁=−7.3 MJ m⁻³ and K₂=−1.25 MJ m⁻³ at 2 K, exceeds by an order of magnitude that in LuFe₆Al₆. Anisotropy within the easy plane in the ferromagnetic state and anisotropy in the paramagnetic range, both absent in LuFe₆Al₆, are observed in UFe₆Al₆.     

Raman and brillouin scattering in a single crystal of K2Hg(CN)4

The temperature dependence of the elastic constants of cubic K₂Hg(CN)₄ has been measured by optical Brillouin spectroscopy in the temperature range from 300-110 K. A decrease of all three elastic constants was found in agreement with the results of ultrasonic measurements. Raman measurements in the temperature range from 300-4 K revealed a splitting of the F_2g modes corresponding to a trigonal distortion of the Hg(CN)₄-tetrahedra in the low temperature phase.     

Tb0.3Dy0.7Fe2合金的本构参数辨识方法研究

建立了一种简便的、适用于磁畴模型应用的Tb_0.3Dy_0.7Fe₂ 合金本构参数辨识方法. 针对Tb_0.3Dy_0.7Fe₂合金磁畴模型中本构参数不明确且直接实验测试困难的问题, 提出了一种数值计算与实验测试相结合的参数辨识方法. 采用坐标变换与绘制自由能等势曲线相结合的方法, 简化了载荷作用下Tb_0.3Dy_0.7Fe₂ 合金内磁畴角度偏转的数值计算, 研究了合金磁畴角度偏转模型的参数依赖性. 在此基础上, 结合简单的实验测试, 建立了Tb_0.3Dy_0.7Fe₂合金各向异性常数K₁ 和K₂、能量分布因子ω、晶轴取向分布的辨识及修正方法. 该方法能够简单、快速地完成Tb_0.3Dy_0.7Fe₂ 合金磁畴模型中本构参数的辨识, 对完善磁致伸缩材料磁畴偏转的数值计算模型非常有意义. 理论分析可为类磁致伸缩材料磁机耦合模型的建立、完善, 以及材料本构参数的辨识、获取提供参考.     

Hyperfine interactions in Zn-doped K2CuF4

The hyperfine fields of Cu²⁺ and F^- ions nearest to a Zn²⁺ ion are measured by a spin echo method in a single crystal of K₂Cu_0.95Zn_0.05F₄. It is shown that the local symmetry due to the Jahn-Teller distortion is practically unaffected by the proximity of Zn²⁺ ions.     

A reduced form of the spin-rotation Hamiltonian for asymmetric-top molecules,with applications to HO2 and NH2

The spin-rotational Hamiltonian for an asymmetric-top molecule in a given vibrational level of an open-shell electronic state may contain more parameters than can be determined from the observed energy levels. This paper describes the reduction of the Hamiltonian by means of a unitary transformation to a form suitable for fitting to observed energies. It is shown that, for molecules of lower than orthorhombic symmetry, there are fewer determinable quadratic spin-rotation parameters than have been used previously. For example, for a molecule belonging to the group C₈, there are four, not five, determinable spin-rotation constants, ?_αβ. Similar indeterminacies exist among the quartic terms of the spin-rotation Hamiltonian. The case of a molecule of orthorhombic symmetry, for which there are six determinable quartic parameters, is considered in detail. The results are applied to the experimental data available on the spin-rotation splittings of the HO₂ and NH₂ radicals in their ground vibrational and electronic states.     

Paramagnetic properties of several rare earth compounds with K3Ln2(NO3)9 structure

We present measurements of the paramagnetic susceptibilities of K₃Pr₂(NO₃)₉ and K₃Sm₂(NO₃)₉, cubic materials with rare earth sites having threefold rotational symmetry about (111). The rare earth environment resembles that of the Ln₂Mg₃(NO₃)₁₂·24H₂O materials, and the magnetic susceptibilities show similarities but also interesting differences with Pr₂Mg₃(NO₃)₁₂·24H₂O and Sm₂Mg₃(NO₃)₁₂·24H₂O. Paramagnetic resonance experiments in K₃La₂(NO₃)₉ doped with these and several heavier lanthanides are also described and compared with theory.     

金属玻璃(Fe1-xCox)78Si10B12的感生各向异性

本文研究了金属玻璃(Fe_1-xCO_x)₇₈Si₁₀B₁₂的磁化感生各向异性、应变感生各向异性随成分和温度的变化。磁化感生各向异性常数K_um为正值,x=0.7时为最大;不可逆的应变感生各向异性常数K_usi为正值,x=0.5时为最大;可逆的应变感生各向异性常数K_usr除了x>0.975区均为负值,在x=0.7时为最大;感生各向异性常数在温度变化时与M_s^α成正比,α在3.4和7.5之间随成分和退火工艺而变化。用短程有序模型解释了部分实验结果。 关键词：     

Coupling of the CDW and the water mode in K2Pt(CN)4Br0.3⋯3.2H2O

In previous work we have observed the amplitude mode of the charge density wave (CDW) in K₂Pt(CN)₄Br_0.3?3.2H₂O (KCP) by means of Raman scattering. New measurements made on deuterated material, K₂Pt(CN)₄Br_0.3?3.2D₂O (KCP1), show the same mode but shifted from 44 to 38 cm_?1, maintaining the symmetry properties and temperature dependence of frequency and linewidth. This considerable isotope effect is interpreted in terms of a coupling of the CDW with the water stretching mode, which by the deuteration is shifted from 3494 cm^?1 in KCP to 2560 cm^?1 in KCP1 according to the change in atomic mass. Both of these modes exhibit A₁(z) symmetry. At 5 K the resulting decoupled frequency of the CDW amplitude mode is 57 cm^?1, and the coupling energy about 140 cm^?1. A discussion of the temperature dependence of various important quantities is given. The present results show that the water molecules, which are located in between the Pt chains are strongly involved in the eigenvector of the CDW amplitude mode.     

分子部分电子态的高阶振动能级和离解能的精确研究

鉴于K₂分子电子态的振动能谱和分子离解能D_e在实际研究和应用中的重要性,应用Sun,Ren等人提出的基于微扰理论的代数方法(AM)和基于AM的代数能量方法(AEM)研究了K₂分子的X¹Σ⁺_g,a³Σ⁺_u,0^-_g,B¹Π_{u< 关键词： 2}分子')" href="#">K₂分子 代数方法 高阶振动能级 离解能     

The Forbidden RotationalQ-Branch of CH3CF3: Torsional Properties and (A1−A2) Splittings

The pure rotational spectrum driven by the small distortion dipole moment perpendicular to the symmetry axis has been investigated between 8 and 18 GHz for CH₃CF₃in the ground vibrational state using a pulsed Fourier transform waveguide spectrometer. This molecule has been selected as a prototype for the case of a symmetric top with small (∼500 kHz) torsional energy splittings in the ground torsional state (ν₆= 0). In this state, six (k± 3 ←k)Q-branch series have been measured for lower stateK= |k| between 3 and 8 with 27 ≤J≤ 75. For (ν₆= 1), three series with lower stateKbetween 5 and 7 with 49 ≤J≤ 66 have been observed. In two of these series, the torsional fine structure extending over ∼6.8 MHz has been fully resolved. The (A₁−A₂) splitting has been measured in the (ν₆= 0) series (K= 6 ← 3) for 37 ≤J≤ 74. The global data set of 443 frequencies included avoided-crossing molecular-beam splittings of Meerts and Ozier (1991.Chem. Phys.152, 241–259) and mm-waveR-branch measurements of Bocquetet al.(1994.J. Mol. Spectrosc.165, 494–499). In a weighted least-squares analysis, a good fit was obtained by varying 18 parameters in a Hamiltonian that represented both the torsional effects and the sextic splittings. Effective values have been determined for both rotational constants, eight torsional parameters including the barrier height, six diagonal centrifugal distortion constants, and two centrifugal distortion constants (? and ?_J) that characterize the (Δk= ±3) matrix elements. The difficulties are discussed that arise in defining a unique model for the torsional terms in the Hamiltonian when a high barrier symmetric top is investigated by distortion moment spectroscopy. The redundancies are investigated that exist in the quartic and sextic Hamiltonian for a near-spherical top such as CH₃CF₃.     

Magnetic properties in silica-coated CoFe2O4 nanoparticles: Quantitative test for a theory of single-domain particles with cubic anisotropy

We report magnetic properties of silica-coated CoFe₂O₄ nanoparticles (about 32 nm) in a wide temperature range (4-700 K). Coating CoFe₂O₄ nanoparticles with amorphous silica yields an assembly of noninteracting single-domain particles with cubic magnetocrystalline anisotropy. We find that the reduced remanence is about 0.81-0.82 at low temperatures (?100 K), very close to the theoretical prediction (0.83) for cubic anisotropy. The room-temperature anisotropy constant K₁ inferred from the data is also in quantitative agreement with the bulk value (1.8×¹⁰⁶ erg/cm³). The current work thus provides a quantitative test for a theory of noninteracting single-domain particles with cubic anisotropy.     

石榴石磁泡薄膜各向异性常数Ku和K1的转矩法测量

本文详细研究了GGG(Gd₃Ga₅O₁₂)单晶基片的磁转矩与其几何参量及有关物理参量的关系,提出了由转矩曲线测量石榴石磁泡薄膜单轴各向异性常数K_u和立方磁晶各向异性常数K₁过程中扣除基片影响的一种方法。在此基础上利用二元回归法由实测的转矩曲线求出K_u和K₁,以及K_u和K₁的温度关系曲线。 关键词：     

High-Resolution Infrared Spectra of the ν2, ν3, ν4, and 2ν3 Bands of SO3

New measurements are reported for the infrared spectrum of sulfur trioxide, ³²S¹⁶O₃, with resolutions ranging from 0.0015 cm⁻¹ to 0.0025 cm⁻¹. Rovibrational constants have been measured for the fundamentals ν₂, ν₃, and ν₄ and the overtone band 2ν₃. Comparisons are made with the earlier high-resolution measurements on SO₃, and the high correlation among some of the constants related to the Coriolis coupling of the ν₂ and ν₄ levels is discussed in order to understand the areas of disagreement with the earlier work. Splittings of some of the levels are observed and the splitting constant for K=3 of the ground state is determined for the first time. Other observed splittings include the K=1 levels of 2ν₃ (l=2), the K=2 levels of ν₃ and ν₄, and the K=3 levels of ν₂. The analysis shows that there are level crossings between the l=0 and l=2 states of 2ν₃ that allow one to determine the separation of the subband centers for these two states even though access to the l=0 state from the ground state is electric-dipole forbidden. This is a generalized phenomenon that should be found for many other molecules with the same symmetry. The l-type resonance constant, q₃, that causes the splitting of the l₃=±1, k=±1 levels of ν₃ also couples the l₃=0 and 2 states of 2ν₃.