共查询到20条相似文献,搜索用时 42 毫秒
1.
L. K. Zarembo S. N. Karpachev T. A. Ludzskaya I. V. Saenko A. I. Yafasov 《Physics of the Solid State》1997,39(4):570-573
The absorption of a magnetoelastic wave and the nonlinear resonance interaction of counterpropagating magnetoelastic waves
in a manganese-zinc spinel single crystal have been investigated near the conjectured spin-reorientational transition. The
convolution signal vanishes near T
tr=291 K; this is explained by the relaxational dynamics of the magnetic mode near the transition. The increase in the strength
of the field corresponding to the maximum of the convolution with decreasing temperature is explained by a change in the demagnetizing
field.
Fiz. Tverd. Tela (St. Petersburg) 39, 652–655 (April 1997) 相似文献
2.
The spectrum of magnetoelastic waves propagating along the magnetic field in an in-plane magnetized ferromagnetic plate is numerically investigated in the exchangeless approximation. No restrictions are imposed either on the field pattern of backward volume magnetostatic waves (BVMSWs) or elastic waves supported by a plate of a given geometry across the plate or on the relationship between the sound velocity v S and the phase velocity of the magnetoelastic waves v=ω/q (ω is the frequency, q is the wave number). The resonance interaction of the BVMSWs and elastic waves is accompanied, as a rule, by the formation of “stop” bands δω that are proportional to the magnetoelastic coupling constant b. When the BVMSWs are in resonance with Lamb and shear elastic modes the values of the magnetoelastic gaps δω at v≈v S turn out to be of the same order. For v≫v S , the efficiency of the interaction between the BVMSWs and transverse Lamb modes is almost one order of magnitude higher. If the frequency spacing Δω between the elastic modes is smaller than the mag-netoelastic gap in the spectrum (Δω≤δω), which takes place, particularly, in the region of crowding the elastic mode spectrum (v≈v S), the resonant interaction results in mixing the dispersion laws for the elastic modes. Namely, a surface mode may transform into a volume one and a shear mode, into the Lamb mode or into a shear mode with another number. The resonance interaction of the shear and Lamb elastic modes not only forms the magnetoelastic gaps δω∼b 2 but also changes the efficiency of elastic wave coupling with the magnetic subsystem. This may show up as the coexistence of the effects of “repulsing” both the dispersion laws and the damping decrements of the elastic waves at the resonance frequency. It is shown that magnetostriction splits the cutoff frequencies of both transverse Lamb modes and shear modes, as well as the long-wave (q → 0) frequency limits f 0 of the BVMSW modes. This may cause the resonance interaction between BVMSW modes of equal evenness in a narrow frequency band Δ∼b near f 0. 相似文献
3.
Surface magnetoelastic Love waves and nonuniform distributions of the magnetization and elastic strains are investigated in
a uniaxial ferromagnetic film on a massive nonmagnetic substrate in a tangential external magnetic field. A new inhomogeneous
phase is predicted having spatial modulation of the order parameter, arising from magnetostrictive coupling of the magnetization
with lattice strains near the interface of the magnetoelastic and elastic media. It is shown that, at some critical magnetic
field H
c, different from the orientational transition field in an isolated sample, a magnetoelastic Love wave propagating parallel
to the magnetization vector in the film plane becomes unstable. The frequency and group velocity of the wave vanish at wave
number k=k
c≠0 and the wave freezes, forming a domain structure localized in the film and adjoining substrate.
Fiz. Tverd. Tela (St. Petersburg) 41, 665–671 (April 1999) 相似文献
4.
A thorough experimental investigation of elastic and magnetoelastic properties for CeAl2 is given. The temperature dependence of the various elastic modes is accounted for with a magnetoelastic coupling of the strain components to crystal field split magnetic ions. Large magnetic field effects for thec
44-mode in various geometries are observed. The rotational invariant magnetoelastic interaction is deduced from the experiment and quantitatively accounted for. Magnetoacoustic analoga of the Faraday and Cotton-Mouton-Voigt effect are observed for the first time in the paramagnetic phase. 相似文献
5.
Z. A. Kazei N. P. Kolmakova I. B. Krynetskii A. A. Sidorenko L. V. Takunov 《Physics of the Solid State》2000,42(2):285-291
The thermal expansion of the DyVO4 crystal has been experimentally and theoretically investigated in the range of the Jahn-Teller structural phase transition. The manifestation of totally symmetric magnetoelastic interactions upon this transition has been studied for the first time. It is found that the temperature dependences of the unit-cell and thermal expansion parameters along the nonactive Jahn-Teller direction in the basal plane for the DyVO4 crystal exhibit characteristic magnetoelastic anomalies at T<T c due to the ordering of quadrupole moments of Dy3+ ions. The magnetoelastic contributions of the totally symmetric εα1 and εα2 and symmetry-lowering εγ modes to the thermal expansion are calculated within the general crystal-field formalism. The total quadrupolar coefficient G γ and magnetoelastic coefficient B γ are determined from the spectroscopic and spontaneous deformation data. It is demonstrated that the thermal expansion of the DyVO4 crystal in the tetragonal and orthorhombic phases is well described in the framework of the unified model using a common set of interaction parameters for both phases. 相似文献
6.
Summary The effects of heat treatments in vacuum on magnetic permeability, Young's modulus and magnetoelastic wave amplitude were
investigated in the amorphous ferromagnetic alloys Fe73.5Cu1Ta3Si15.5B7 and Fe73.5Cu1W3Si15.5B7 where tantalum or tungsten replaces niobium, which was generally used with the same atomic fractions of the other elements.
The stress sensitivity coefficient was also theoretically deduced in its developmentvs. the applied magnetic bias field. Structural relaxation and crystallization consequences are evidenced. Moreover an already
predicted relation between the maximum of magnetoelastic wave amplitude and the minimum of stress sensitivity coefficient
was confirmed. 相似文献
7.
Brillouin scattering from thermally excited magnons and ferromagnetic resonance are used to determine the spin wave dispersion
of the low-frequency spin wave branch in FeBO3, a transparent weak ferromagnet. In addition to the dominant exchange and Zeeman contributions, the investigation takes into
account magnetic dipole and magnetoelastic interactions. Due to the antisymmetric exchange enhancement the material exhibits
a broad spin wave band and a large gap energy at small magnetic fields. Competing directional dependences of the dipole and
the exchange energy produce a degeneracy of spin waves with a certain magnitude of the wavevector propagating in different
directions. The gap energy is shown to be due to magnetoelastic coupling, whereas the contribution of the anisotropy in the
easy plane is negligible atT=300 K. 相似文献
8.
Kh. G. Bogdanova A. R. Bulatov V. A. Golenishchev-Kutuzov A. A. Potapov A. E. Usachev 《Bulletin of the Russian Academy of Sciences: Physics》2009,73(8):1019-1021
The peculiarities of the phase transitions in La0.825Sr0.175MnO3 single crystal have been investigated by acoustic methods at the frequency f = 770 MHz. Generation of a magnetoelastic wave near the phase transition at 305 K is revealed, which is assigned to quasi-transverse
modes. The most likely cause of the phase transition near T = 305 K and the formation of the quasi-transverse mode is the suppression of local Jahn-Teller distortions. 相似文献
9.
This paper presents the results of investigation on the influence of temperature on magnetoelastic characteristics of the
two ring-shaped cores, made of Fe70Ni8Si10B12 amorphous alloy. The cores were annealed for 1 h at 350 and 400°C, respectively. The compressive force F was applied perpendicular to the direction of the magnetizing field H in the sample. Special cylindrical backing enables application of the uniform compressive stress σ to the wound ring sample. A resistive furnace heated the experimental set-up. Results presented in the paper indicate a significant
influence of the temperature on the magnetoelastic characteristics of Fe70Ni8Si10B12 amorphous alloy. Information about the magnetoelastic characteristics of this material may be useful in the magnetoelastic
sensor development. Also this will create new possibilities in the development of physical model of magnetoelastic effect.
相似文献
10.
V. I. Boldyrev A. S. Veksler A. A. Gavrilyuk S. M. Zubritskii A. L. Petrov M. V. Pinegin 《Russian Physics Journal》1999,42(9):818-821
The effect of thermomagnetic treatment temperature on the speed of magnetoelastic vibrations propagating in aFe
81.5
B
13.5
Si
3
C
2 metal alloy is investigated. A minimum is found in the plot of the dependence of the speed of magnetoelastic vibrations on
the thermomagnetic treatment temperature. No minimum is observed in this dependence for amorphous metal alloys treated without
magnetic field. It is found that the dependences of the speed of magnetoelastic vibrations on the external magnetic field
differ for samples treated differently. The results obtained are explained based on concepts of reorganization of the domain
structure of the samples under study.
Irkutsk State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 46–49, September, 1999. 相似文献
11.
Raman-Nath acoustooptical diffraction was experimentally revealed in easy-plane antiferromagnet α-Fe2O3. The diffraction is due to linear modulation of the polarizations of the optical normal modes propagating along trigonal axis C3 of the crystal due to oscillations of the antiferromagnetism vector L caused by magnetoelastic interaction. The dependence of the diffraction parameters on a dc magnetic field H ⊥ applied in the basal plane was studied. The dependence obtained is in good agreement with the field dependence of the exchange enhancement coefficient of magnetoelastic coupling in fields higher than that at which hematite transforms to a single-domain state (H D ~ 1.8 kOe). for a sound flux power of about 1 W/cm2 in a sample, the maximum intensity of the diffracted wave at H ⊥ = H D is about 0.9% of the input light intensity and its polarization is perpendicular to that of the incoming linearly polarized wave. The results obtained agree qualitatively with the theory of acoustooptical diffraction in antiferromagnets and confirm the antiferromagnetic mechanism of diffraction in the experimental geometry under study. 相似文献
12.
M. Dahl G. Janotta G. Schaack Shi Shan 《Zeitschrift für Physik B Condensed Matter》1989,76(3):327-334
The magnetic splitting of triply degenerate (T
2g
)-phonons in the cubic Rare Earth compound dysprosium-aluminum-garnet could be observed making use of the polarization properties of the Raman-effect.The theoretical predictions of a phenomenological symmetry analysis are compared to a more detailed microscopic treatment of the observations in terms of the magnetoelastic interaction. 相似文献
13.
The polarized Raman spectra of LiTbF4 have been investigated at several temperaturesT150 K, and the temperature dependence of the selfenergies of optical phonons due to the magnetoelastic interaction have been determined. The sizes of these temperature shifts, of the magnetic phonon splittings and of the level repellings between resonant optical phonons and crystal field states have been calculated using the theory of magnetoelastic interaction by Fulde and Thalmeier without any adjustable parameters, considering the modulation of the crystalline electric field by the optical phonons. The phonon modes of LiTbF4 have been determined in a rigid-ion approximation. Reasonable to good agreement with the experimental results has been obtained for most of the phonon modes. 相似文献
14.
15.
Hans-Joachim Hinz 《Zeitschrift für Physik B Condensed Matter》1980,38(2):111-112
Electron energy loss measurements with 50 keV electrons have been performed in order to investigate the influence of crystal orientation on the volume plasmon excitation of Germanium. An anisotropy of the excitation probability is found in so far as the quotientI
vol/I
el (I
vol=intensity of the volume plasmon at 16.2 eV,I
el=elastic intensity) is dependent on the direction of the plasmon wave vector in the crystal. 相似文献
16.
《Journal of magnetism and magnetic materials》2001,236(3):267-271
The magnetoelastic properties of GdCu2 have been investigated by thermal expansion and magnetostriction measurements. GdCu2 orders antiferromagnetically with a noncollinear magnetic structure. The anisotropic magnetostriction is of similar magnitude as in other RCu2 compounds and can be explained by a contribution of the bilinear exchange interaction to the magnetoelastic energy. For several compounds this contribution is as important as the single ion magnetoelastic exchange. The pressure dependence of the Néel temperature of GdCu2 is found to be in agreement with the data of thermal expansion. 相似文献
17.
A. V. Andrienko 《Journal of Experimental and Theoretical Physics》2000,90(3):508-516
Parametric excitation of magnetoelastic waves was investigated in the easy-plane antiferromagnet α-Fe2O3 by parallel and perpendicular microwave pumping over a wide range of frequencies, magnetic fields, and temperatures, and the parametric resonance thresholds were measured. The frequencies of the natural magnetoelastic vibrations of the sample were investigated as a function of the magnetic field and temperature. The results of the measurements were used to calculate the parameters of the magnetoelastic wave spectrum and the rate of relaxation of the excited quasi-phonons. Possible mechanisms for quasi-phonon damping were analyzed. 相似文献
18.
The interaction of a partially ionized continuum gas with a negatively charged electrode is investigated theoretically. It is supposed that ld ? 1, where ld is the Debye length, l is the mean-free-path. The self-consistent solution is given for two cases: lI ? l and lI ~ l, lI is the effective ionisation length. The matched asymptotic expansions method is used. The Bohm sheath criterion is shown to be satisfied automatically in the considered cases. 相似文献
19.
Changes in the magnetic moment of crystalline FeBO3 when an antiferromagnetic resonance is excited in it are studied. This done using a SQUID magnetometer in combination with
a microwave spectrometer. At temperatures T>15 K a reduction in the total magnetic moment of the sample is observed when an antiferromagnetic resonance is excited in
it. At liquid helium temperatures, an induced rise in the sample magnetic moment was observed. This type of magnetization
of the sample can be explained qualitatively if it is assumed that under antiferromagnetic resonance excitation conditions,
magnetoelastic modes with high wave numbers are excited along with magnons. Efficient excitation of magnetoelastic modes under
antiferromagnetic resonance conditions is confirmed by the experimental observation of a size effect in thin, high quality
single crystal slabs of FeBO3.
Zh. éksp. Teor. Fiz. 115, 1107–1115 (March 1999) 相似文献
20.
A phenomenological estimate is derived such that the binding energies of dimesons are expressed as combinations of masses
of different mesons and baryons. The estimate is almost model-independent, the only major assumptions being that the wave
functions of the two light quarks in Λ
c
, Λ
b
and in the and dimesons are very similar, and that for heavy quarks the QQ interaction is half as strong as the interaction. We get (I = 0, J = 1) bound by about 100 MeV and unbound.
Received July 4, 2000; revised November 28, 2000; accepted for publication February 5, 2001 相似文献