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1.
The behavior of isotherms of the magnetization σ(H) and the longitudinal λ‖ and transverse λ⊥ magnetostriction of the polycrystalline ferrite CoFeCrO4 with frustrated magnetic structure has been investigated for the first time in magnetic fields up to H=50 kOe at T=4.2 K. It is found that the magnetization grows with increasing field due to two different paraprocesses.
Fiz. Tverd. Tela (St. Petersburg) 41, 2042–2043 (November 1999) 相似文献
2.
B. S. Dumesh M. I. Kurkin S. V. Petrov A. M. Tikhonov 《Journal of Experimental and Theoretical Physics》1999,88(6):1221-1228
The spectrum and intensities of NMR lines are investigated experimentally and theoretically for excitation by an alternating
magnetic field h‖ parallel to a static field H in the quasi-one-dimensional, six-sublattice antiferromagnet CsMnBr3. According to theory, two new NMR lines, which are not excited by a transverse magnetic field h
⊥, are observed near the phase transition from triangular to collinear structure (H=H
c
) [JETP 86, 197 (1998)].
Zh. éksp. Teor. Fiz. 115, 2228–2241 (June 1999) 相似文献
3.
A. A. Demidov I. A. Gudim E. V. Eremin 《Journal of Experimental and Theoretical Physics》2012,114(2):259-272
The magnetic properties of ferroborate single crystals with substituted compositions Nd1 − x
Dy
x
Fe3(BO3)4 (x = 0.15, 0.25) with competing exchange Nd-Fe and Dy-Fe interactions are investigated. For each composition, we observed a
spontaneous spin-reorientation transition from the easy-axis to the easy-plane state and step anomalies on the magnetization
curves for the spin-flop transition induced by a magnetic field B | c. The measured parameters and effects are interpreted using a unified theoretical approach based on the molecular field approximation
and on calculations performed in the crystal-field model for the rare-earth ion. The experimental temperature dependences
of the initial magnetic susceptibility from T = 2 K to T = 300 K, anomalies on the magnetization curves for B | c in fields up to 1.8 T, and their evolution with temperature, as well as temperature and field dependences of magnetization
in fields up to 9 T are described. In the interpretation of experimental data, the crystal-field parameters in trigonal symmetry
for the rare-earth subsystem are determined, as well as the parameters of Nd-Fe and Dy-Fe exchange interactions. 相似文献
4.
Summary In this work we report on the anisotropic physical properties of silver-sheathed Bi-2223 tapes fabricated by means of hot
extrusion and repeated pressing and sintering processes. The obtained Bi-2223/Ag short tapes, having critical current densitiesJ
c of 20–30 kA/cm2 at 77 K, 0 T, were measured in external magnetic fields up to 0.5T applied in two different orientations (i.e. μ0H‖(a,b)-planes and μ0H ⊥(a,b)-planes). The magnetic characterizations were performed in a wide range of temperatures and magnetic fields to study
the first magnetization curve of tapes evaluating the lower critical fields μ0Hc1⊥ab and ⊥0Hc1#x2016;ab and their dependences on temperature. TheJ
c values at different fields in the temperature range 4.6–90 K, calculated from the magnetization data by the critical state
model, are also presented.
Paper presented at the ?VII Congresso SATT?, Torino, 4–7 October 1994. 相似文献
5.
6.
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
7.
A. Michels J. Weissmüller R. Birringer 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(4):533-540
Based on a micromagnetics model, we develop a method through which quantitative information on the volume-averaged mean-square
magnetostatic stray field 〈|H
b
d|2〉
v due to non-zero divergences of the magnetization M within the bulk of a ferromagnetic body can be obtained by analysis of magnetic-field-dependent small-angle neutron scattering
data. In the limit of high applied magnetic field H
a, when the direction of M deviates only sligthly from H
a, we have estimated a lower bound for 〈|H
b
d|2〉
v as a function of the external field, and we have applied the method to bulk samples of nanocrystalline electrodeposited Ni
and Co and coarse-grained polycrystalline cold-worked Ni. The root-mean-square magnetostatic stray field, which is inherent
to a particular magnetic microstructure, shows a pronounced field dependence, with values ranging from about 5 to 50mT. Even
at applied fields as large as 1.7T, the quantity μ〈|H
b
d|2〉1/2
v of nanocrystalline Co is still 24mT, which suggests that contributions to the total magnetostatic field originating from
the bulk are significant in nanocrystalline ferromagnets; therefore, 〈|H
b
d|2〉
v cannot be ignored in the interpretation of e.g. measurements of magnetization or spin-wave resonance. A comparison of 〈|H
b
d|2〉
v with the volume-averaged mean-square anisotropy field reveals that both quantities are of comparable magnitude.
Received 25 April 2002 Published online 31 October 2002
RID="a"
ID="a"e-mail: anmi@nano.uni.saarland.de 相似文献
8.
A. D. Balaev V. A. Gavrichkov S. G. Ovchinnikov V. K. Chernov T. G. Aminov G. G. Shabunina 《Journal of Experimental and Theoretical Physics》1998,86(5):1026-1029
In the magnetic field range ΔH=8–60 kOe we observed and studied the anomalous oscillations in the magnetic field dependence of the resistance and magnetization
of single crystals of n-HgCr2Se4. The absence of periodicity in 1/H in the ΔH=8–20 kOe range can be explained by the non-Fermi-liquid behavior of the electron subsystem and agrees with the theory of
the de Haas-van Alphen in systems with intermediate valence. In stronger fields, ΔH=20–60 kOe, the amplitude of the fundamental harmonic decreases, with the number and amplitude of the higher-order harmonics
increasing. As a result, noise is superimposed on the signal as magnetic field strength grows. The temperature dependence
of the magnetization is the sum of the monotonic spin-wave contribution and the oscillating part.
Zh. éksp. Teor. Fiz. 113, 1877–1882 (May 1998) 相似文献
9.
Yu. I. Man’kov 《Physics of the Solid State》1999,41(4):582-588
The effect of conduction electrons on the magnetization curve of a metallic ferromagnet with surface pinning of the magnetic
moment is investigated theoretically. The electronic contribution is due to the rearrangement of the discrete spectrum of
charge carriers trapped by the nonuniform magnetic induction of such a ferromagnet, and it is a kind of diamagnetic effect
that appreciably decreases the volume-averaged magnetization of the ferromagnet. A powerlaw dependence H
−3/4 on the external magnetic field H is obtained according to the law of magnetization approach to saturation. This dependence is due to the contribution of the
conduction electrons.
Fiz. Tverd. Tela (St. Petersburg) 41, 647–653 (April 1999) 相似文献
10.
The field, temperature, and angular dependences of longitudinal λ‖ and transverse λ⊥ magnetostriction in single-crystal DyFe11Ti are investigated. Tensometric measurements were made in the temperature range from 78 to 300 K in magnetic fields up to
12 kOe. Measurements of the magnetostriction of single-crystal DyFe11Ti, YFe11Ti, and LuFe11Ti imply that the sublattice of 3d transition metals makes only a small contribution to the magnetostriction in compounds RFe11Ti, and that the primary contribution to the magnetostriction of these compounds comes from the rare-earth metal sublattice.
The primary microscopic mechanism for magnetostriction is single-ion magnetostriction caused by the interaction of the anisotropic
orbital electron cloud around the Dy3+ magnetic ion with the crystal field of the lattice.
Fiz. Tverd. Tela (St. Petersburg) 41, 1647–1649 (September 1999) 相似文献
11.
The features of magnetization of rare-earth multiferroic PrFe3(BO3)4 with the singlet ground state have been investigated theoretically. The magnetic anisotropy of the crystal has been studied. The temperature dependences of anisotropy constants have been calculated. The phase H-T diagram has been constructed. The dependences of the behavior of magnetization vectors of magnetic sublattices on the external magnetic field have been obtained. The magnetoelectric effect has been investigated, and the dependences of polarization on the temperature and field have been found for its various orientations. The theoretical data have been compared with the experimental data and their good agreement has been established. 相似文献
12.
13.
A theory of μSR method is developed for uniaxial anisotropic high-T
c superconductors. In two extreme cases ofH
ext‖c
andH
ext⊥c
analytical formulas are obtained which makes it possible to determine from the position of van Hove singularities in the
Fourier-spectrum of muonium polarization, the type and parameters of the vortex lattice, such as λ
ab
(λ
c
). In caseH
ext≲H
c2 we obtained the shape of the Fourier-spectrum in analytical form and the simple method of determining the Ginsburg-Landau
parameter κ.
Convenient expressions for numerical calculations are obtained for the arbitrary orientation of the external field, and an
algorithm is provided to compute the mean fieldB, the vortex lattice parameters and the bulk field distribution in anisotropic superconductor. The Fourier spectrum of polarization
based on these calculations can be used to independently check the validity of the high-T
c parameters determination for “appropriate” orientations. 相似文献
14.
M. A. Zelikman 《Technical Physics》1997,42(9):1019-1026
The behavior of planar (laminar) vortices in a three-dimensional, ordered Josephson medium as a function of the parameter
I, which is proportional to the critical junction current and the cell size, is investigated with allowance for pinning due
to the cellular structure of the medium. The minimum possible distances between two isolated vortices are calculated. A system
of vortices formed in a sample in a monotonically increasing external magnetic field is analyzed. The minimum distance from
the outermost vortex to the nearest neighbor is proportional to I
−1.1. For I⩽1.3 each vortex contains a single flux quantum Φ0, and the distance between them does not decrease in closer proximity to the boundary but remains approximately constant,
implying that the magnetic field does not depend on the coordinate in the region penetrated by vortices. These facts contradict
the generally accepted Bean model. The sample magnetization curve has a form typical of type II superconductors. Allowance
for pinning raises the critical field H
c and induces a sudden jump in the curve at H=H
c.
Zh. Tekh. Fiz. 67, 38–46 (September 1997) 相似文献
15.
Kh. G. Bogdanova V. A. Golenishchev-Kutuzov V. E. Leont’ev M. R. Nazipov M. M. Shakirzyanov M. I. Kurkin V. V. Nikolaev 《Journal of Experimental and Theoretical Physics》1997,85(5):1001-1006
Ultrasound damping at T=4.2 K in single crystal easy-plane antiferromagnetic KMnF3 is studied experimentally as a function of the magnitude and direction of a constant magnetic field H at frequencies of 640–670 MHz, corresponding to the frequencies of nuclear spin waves. Two experimental situations are examined:
in the first, the vector H lies in the easy magnetization plane (001), and in the second, H forms an angle with (001). For longitudinal ultrasound waves propagating along the hard magnetization axis [001], it is found
that the damping depends resonantly on the magnitude of the field H. In the first case a single damping maximum is observed, and in the second, two damping peaks that are well resolved with
respect to the field. The angular dependence of the resonance damping signals on the direction of the constant magnetic field
is found to have a 90° periodicity in all cases. The observed effects are explained by resonant ultrasonic excitation of nuclear
spin waves. On the basis of an analysis of the magnetoacoustic interaction energy, it is shown that in the first case, nonzero
oscillations of the antiferromagnetism vector L occur only in the basal plane, while in the second, oscillations of L occur both in the basal and a vertical plane, which are associated, respectively, with two branches of the nuclear spin waves.
It is also shown that the 90° periodicity in the angular dependence of the damping signals is associated with a fourth order
[001] axis.
Zh. éksp. Teor. Fiz. 112, 1830–1840 (November 1997) 相似文献
16.
D. É. Fel’dman 《Journal of Experimental and Theoretical Physics》1999,88(6):1170-1178
The critical behavior of the transverse (with respect to the field) magnetization component in classical degenerate magnets
with only nearest-neighbors interaction in a uniaxial random magnetic field at zero temperature is found exactly. For a Gaussian
distribution of the random field the asymptotic transverse magnetization in strong fields does not depend on the dimension
of the space and is of the form m
⊥ ∝ 1nh
0/h
0
2
, where h
0 is the width of the distribution. For a bimodal distribution, where only the field direction is random and the amplitude
is fixed, the transverse magnetization behaves as m
⊥∝exp(−const/(H
c
−H)
D/2), where H is the amplitude of the random field, D is the dimension of the space, and H
c
is the critical field.
Zh. éksp. Teor. Fiz. 115, 2143–2159 (June 1999) 相似文献
17.
A calculation is performed to determine the transverse electric field Ey formed in quasi-two-dimensional superlattices in a strong drift field Ex and a weak magnetic field that is perpendicular to the plane of the superlattice (H‖OZ). When the electronic energy spectrum is nonadditive, the field Ey includes both the Hall factor and a spontaneous transverse electric field that exists whetherH is present or not. The situation when the specimen is in a closed circuit with a resistor on the OY axis is examined. As
the function Ex, the field Ey is multivalued (multistable) and variable. The stability of the branches of the function Ey(Ex) is determined using a specially introduced (kinetic) “potential” whose minimum corresponds to the steady state of a nonequilibrium
electron gas.
Volgograd State Pedagogical University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 46–51,
July, 1996. 相似文献
18.
L. K. Aminov A. A. Ershova V. N. Efimov S. L. Korableva I. N. Kurkin B. Z. Malkin A. A. Rodionov 《Physics of the Solid State》2010,52(10):2070-2075
The EPR spectra of Ce3+ impurity ions in LiYF4, LiLuF4, and LiTmF4 double-fluoride single crystals have been investigated at a frequency of ∼9.3 GHz in the temperature range 5–25 K. The effective
g factors of the ground Kramers doublet of the cerium ions in three crystals are close to each other (g
‖ = 2.737, g
⊥ = 1.475 for LiYF4:Ce3+). A superhyperfine structure of the EPR spectrum of Ce3+ ions in the LiTmF4 Van Vleck paramagnet has been observed in the external magnetic field B oriented along the crystallographic axis c (B ‖ c). The superhyperfine structure of the EPR soectra of the Ce3+ ions in the LiYF4 and LiLuF4 diamagnetic matrices is resolved for B ⊥ c. Possible factors responsible for this pronounced difference in the properties of the systems studied have been discussed. 相似文献
19.
V. P. D’yakonov V. I. Markovich V. L. Kovarskii A. V. Markovich M. Borowiec A. Endzheichak G. Szymczak 《Physics of the Solid State》1998,40(12):2017-2020
This paper presents the results of a study of the thermal properties of monoclinic single-crystal RbDy(WO4)2 at temperatures of 2–15 K and in magnetic fields up to 6 T. From the results of measurements of the heat capacity and thermograms,
two structural phase transitions are detected, at T
c1=4.9 K and T
c2=9.0 K. The transformation from the high-temperature phase to the low-temperature phase occurs via an intermediate phase.
The field dependences of the critical temperatures are found for various magnetic-field orientations. H-T phase diagrams are constructed for H‖a and H‖c. An anomalous increase (by almost an order of magnitude) of the relaxation time of the system, associated with structural
instability of the crystal lattice, is detected in the region of the structural phase transitions. A symmetry analysis is
carried out, and possible crystal structures of the low-temperature phase are indicated.
Fiz. Tverd. Tela (St. Petersburg) 40, 2221–2225 (December 1998) 相似文献
20.
B V B Sarkissian A K Grover G Balakrishnan Ravi Kumar P L Paulose R Vijayaraghavan V Sankaranarayanan C K Subramanian 《Pramana》1992,38(6):641-667
The results of experimental studies on hysteresis in magnetization, thermomagnetic history effects, anomalous variations in
magnetic hysteresis curves and the decay rates of magnetization obtained under different thermomagnetic histories in specimens
of conventional and high temperature superconductors are presented. The Bean’s critical state model is considered adequate
to explain magnetic behaviour in conventional hard superconductors. The similarity in the general features of the results
of different experiments on specimens of the two families of superconductors underscores the efficacy of the said model to
understand some aspects of the macroscopic magnetic response of high temperature superconductors as well. For instance, the
isothermal magnetization hysteresis loop which comprises of magnetization curves along forward (−H
max to +H
max) and reverse (+H
max to −H
max) paths define an envelop within which all isothermal magnetization data along different thermomagnetic histories lie. There
exist inequality relationship between various field values identified asH
peak,H
I,H
II etc. in isothermal magnetization hysteresis as well as magnetic relaxation data. The entire field span of an isothermal magnetization
hysteresis data set can be considered to comprise of three parts corresponding to (M
rem(H)−M
FC(H)+M
ZFC(H)) being equal to, less than or greater than zero, whereM
rem(H) are the remanent magnetization values obtained on reducing field to zero after having the specimen in different applied
field (H) values. There are, however some situations amongst thermomagnetic history effects in specimens which show incomplete flux
trapping on field cooling, where the critical state model has been found inadequate. 相似文献