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1.
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
2.
An effect of nonpolarized white light on the modulated magnetic structure of a FeBO3:Mg single crystal, which arises in this light-plane weak ferromagnet in the low temperature range during technical magnetization,
has been revealed. It has been found that the degree of the light action on the magnetic state of FeBO3:Mg depends both on its duration and on the orientation of the spontaneous magnetization vector M of the crystal during illumination. Interpretation of the results obtained has been performed in the context of the “magnetic
ripple” theory on the assumption that the absorbed light induces additional uniaxial magnetic anisotropy in the easy plane
of the crystal and that the anisotropy axis is collinear to the vector M during illumination. 相似文献
3.
We have performed measurements of the magnetization and differential magnetic susceptibility of Dy0.62Y2.38Fe5O12 single crystals in pulsed magnetic fields up to 45 T at liquid-helium temperature for three orientations of the external
field: H‖[100], H‖[110], and H‖[111]. It was found that the magnetization reversal in the rare-earth magnetic subsystem occurs via several phase transitions,
whose number depends on the direction of the external field, as is characteristic for Ising magnets. The anomalies in the
field dependences of the magnetization are interpreted on the assumption of quasi-Ising ordering of the rare-earth ions.
Pis’ma Zh. éksp. Teor. Fiz. 67, No. 8, 552–556 (25 April 1998) 相似文献
4.
A study is made of the temperature and field dependences of the anisotropic magnetization of a quasi-one-dimensional charge-density-wave
conductor — the blue bronze K0.3 MoO3. Nonlinearity of the magnetization curves is observed at temperatures below 100 K. The temperature and field dependences
of the magnetic moment show the effect to be of a collective nature.
Pis’ma Zh. éksp. Teor. Fiz. 68, No. 4, 281–286 (25 August 1998) 相似文献
5.
The frequency of orientational quantum oscillations of the magnetization near impurity-ion clusters with Ising properties
in a saturated magnetic crystal is calculated. It is noted that in compounds of the type HoxY3−x
Fe5O12, where magnetic phase transitions are observed, additional magnetization reversal and magnetic resonance features due to
mesoscopic oscillations of the magnetization can be observed at low concentrations x<0.001 and cryogenic temperatures in fields comparable to the intersublattice exchange interaction field.
Pis’ma Zh. éksp. Teor. Fiz. 65, No. 6, 445–448 (25 March 1997) 相似文献
6.
This paper describes the first investigations of the process of pulsed 180° magnetization reversal in iron borate in the presence
of a transverse magnetic field. How the intensity of magnetoelastic oscillations depends on the amplitude of the magnetization
reversal field and the duration of the primary period of the transient process is studied, and also the analysis of hodographs
of the magnetization vector, which show that the primary reason why the pulsed magnetization reversal curve exhibits a kink
is a decrease in the energy lost to excitation of magnetoelastic oscillations, caused by lagging of the elastic subsystem
of the crystal behind the magnetic subsystem for magnetization reversal times less than 13–16 ns.
Fiz. Tverd. Tela (St. Petersburg) 40, 305–309 (February 1998) 相似文献
7.
The effect of the interaction of Abrikosov vortices with the magnetization on the longitudinal vortical instability in a layered
ferromagnet-type-II superconductor structure is analyzed. It is shown that in the vicinity of the orientational phase transition
in the magnet, where the transverse magnetic susceptibility is large, the magnitude of the longitudinal critical current in
the structure can be almost 1.5 times smaller than in the isolated superconductor. The reason for this is compensation of
stray field sources outside the superconductor by “magnetic charges” arising from a jump in the transverse magnetization on
the surface of the magnet. A structure is considered in which the thickness of the superconductor significantly exceeds the
London penetration depth of the magnetic field and the wavelength of the critical mode. For this reason (in light of the absence
of high-quality bulk high-temperature superconductors), to experimentally study the described phenomenon it is necessary to
use conventional low-temperature superconductors.
Fiz. Tverd. Tela (St. Petersburg) 39, 231–235 (February 1997) 相似文献
8.
The conditions for synthesis of solid solutions in the quasibinary CrTe-MnTe system are analyzed. A study is made of the effect
of cation substitution on the properties of the synthesized solid solutions in measurements of magnetization, magnetic susceptibility,
electrical conductivity, and the Seebeck coefficient at temperatures of 80–750 K.
Fiz. Tverd. Tela (St. Petersburg) 39, 320–324 (February 1997) 相似文献
9.
A. A. Bukharaev D. V. Ovchinnikov N. I. Nurgazizov E. F. Kukovitskii M. Klaiber R. Wiesendanger 《Physics of the Solid State》1998,40(7):1163-1168
Isolated Ni nanoparticles were studied in situ by atomic and magnetic force microscopy in the presence of an additional external field up to 300 Oe. By comparing topographic
and magnetic images, and also by computer modeling of magnetic images, it was established that particles smaller than 100
nm are single-domain and easily undergo magnetic reversal in the direction of the applied external magnetic field. For large
magnetic particles, the external magnetic field enhances the magnetization uniformity and the direction of total magnetization
of these particles is determined by their shape anisotropy. Characteristics of the magnetic images and magnetic reversal of
particles larger than 150 nm are attributed to the formation of a vortex magnetization structure in these particles.
Fiz. Tverd. Tela (St. Petersburg) 40, 1277–1283 (July 1998) 相似文献
10.
Experimental and theoretical investigations are made of the magnetization of solidified dielectric colloids prepared using
single-domain magnetite particles with randomly oriented axes of easy magnetization. A method is proposed to calculate the
magnetization curves with allowance for blocking of the magnetic moments of particles and magnetic-dipole interparticle interactions.
It is shown that magnetic colloids with an extremely low remanent magnetization (a few tens of amps per meter) may be obtained.
Fiz. Tverd. Tela (St. Petersburg) 40, 1062–1067 (June 1998) 相似文献
11.
N. F. Kubrakov A. K. Zvezdin K. A. Zvezdin V. A. Kotov R. Atkinson 《Journal of Experimental and Theoretical Physics》1998,87(3):600-607
The change in the reflectivity of a metallic magnetic multilayer that exhibits giant magnetoresistance for a monochromatic
electromagnetic plane wave with polarization along the magnetization (s polarization) in response to a change from the antiferromagnetic magnetic configuration of the multilayer to the ferromagnetic
configuration is investigated. This magneto-optical effect is treated in the effective-medium approximation, in which the
dielectric constant needed is found analytically with consideration of the interface roughness scattering of electrons. It
is shown in the example of an Fe/Cu multilayer that the effect amounts to ∼0.7%. The representation found for the complex
conductivity is convenient in a special case for investigating the magnetoresistive effect.
Zh. éksp. Teor. Fiz. 114, 1101–1114 (September 1998) 相似文献
12.
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
13.
I. O. Troyanchuk N. V. Samsonenko G. Shimchak A. Nabyalek 《Physics of the Solid State》1997,39(1):101-103
The magnetic properties of Eu1−x
CaxMnO3 have been investigated. As the calcium content increased up to x=0.2, the magnetization and the blocking temperature of the magnetic moments of clusters increased and the magnetic anisotropy
decreased. As the calcium content increased further, the magnetization decreased, while the “freezing” temperature of the
magnetic moments increased. Anomalies of the magnetic properties were observed in compositions with x=0.4 and 0.5 at T=40 K; these anomalies are attributed to a transition to the antiferromagnetic state in the charge-ordered phase.
Fiz. Tverd. Tela (St. Petersburg) 39, 117–120 (January 1997) 相似文献
14.
A contribution to electromagnetic power losses, additional to the losses due to eddy currents and exhibiting a resonance frequency
dependence with the main maximum near 1 GHz, has been observed for the ferromagnetic alloy Pd2AuFe in the frequency range 0.9 MHz–10 GHz in the absence of an external constant magnetic field. Investigations performed
in a dc magnetic field show that this effect is a natural ferromagnetic resonance due to intradomain magnetization precession
in the effective magnetic-anisotropy field.
Fiz. Tverd. Tela (St. Petersburg) 40, 1900–1904 (October 1998) 相似文献
15.
A theory of the de Haas-van Alphen effect in type-II superconductors is proposed. The effect of the electron scattering by
nonmagnetic impurities in a magnetic field in the potential produced by a nonuniform distribution of the order parameter in
a mixed state is investigated. The magnitude of the order parameter and quasiparticle density of states are determined from
the solution of the system of Gor’kov equations. It is shown that in the presence of even a small amount of impurities, the
superconducting state near the upper critical field is gapless. In this region, the oscillatory (in the magnetic field) contribution
to the density of states and the characteristic damping of the amplitude of the magnetization oscillations in the superconducting
state are found.
Zh. éksp. Teor. Fiz. 112, 1873–1892 (November 1997) 相似文献
16.
Angular dependences of the magnetization hysteresis loops have been studied at T=77 K on YBCO single crystals exhibiting the peak effect. The peak effect is shown to be related to the pinning of longitudinal
vortices along the c axis at twin boundary-type ordered defects. The behavior of the peak effect at intermediate angles is explained by anisotropic
magnetic field penetration into quasi-two-dimensional superconductors. In thin crystals with a dilute ordered-defect structure
this can result in an enhanced peak effect due to formation of a vortex kink structure and to “internal” pinning of transverse
vortex segments at Cu-O sheets.
Fiz. Tverd. Tela (St. Petersburg) 39, 425–431 (March 1997) 相似文献
17.
The influence of thermal fluctuations on magnetization-reversal processes in ultrathin magnetic particles is investigated
on the basis of a numerical solution of the Landau-Lifshitz-Gilbert equations taking account the thermal-activation fluctuation
field. It is shown that for nanoparticles there exists a region of magnetic and geometric parameters where a strong jump-like
instability of the critical field for magnetization reversal arises. This instability is due to the thermally activated transformation
of magnetization configurations far from the switching threshold. The thermal-instability mechanism described is important
for particles of much larger sizes than for the single-mode Néel-Brown instability.
Pis’ma Zh. éksp. Teor. Fiz. 69, No. 8, 555–560 (25 April 1999) 相似文献
18.
A. F. Andreev 《JETP Letters》1996,63(9):758-762
The macroscopic magnetic fields arising in the space outside or in the bulk of an antiferromagnet in the absence of external
currents are a result of surface magnetization. The general problem of determining these fields is formulated. It is shown
that the field distribution near special lines on the surface is monopolar. An experimental study of the field makes it possible
to determine the surface magnetization on the faces of an antiferromagnetic crystal.
Pis’ma Zh. éksp. Teor. Fiz. 63, No. 9, 724–728 (10 May 1996) 相似文献
19.
C. Caizer I. Hrianca 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,31(3):391-400
We have studied the magnetization of a system of γ-Fe2O3 (0.68 vol.%) nanoparticles isolated in an SiO2 amorphous matrix placed in an alternating magnetic field with a frequency of 640 Hz and in the temperature range of (77-300)
K. Compared to temperatures closer to 300 K (where the system has a superparamagnetic behaviour), at lower temperatures, the
magnetization has a dynamic hysteresis loop due to the magnetization's phase shift between the field and the magnetization.
The delay of the magnetization (attributed to the Néel relaxation processes) increases with the decrease of temperature. It
has been shown that the relaxation time resulting from the Néel theory is determined by an effective anisotropy constant (
K
) that takes into account the magnetocrystalline anisotropy, as well as the shape, surface and strain anisotropies. In the
following we will show that the surface and strain anisotropy components have the most significant influence. When the temperature
decreases from 300 to 77 K, the relative increase of the saturation magnetization of the nanoparticles is much higher than
that of the (spontaneous) saturation magnetization of bulk γ-Fe2O3. This increase is due to the increase of the mean magnetic diameter of the particles attached to the core of aligned spins,
from 10.16 nm to 11.70 nm, as a result of the modification of the superexchange interaction in the surface layer.
Received 25 April 2002 / Received in final form 11 August 2002 Published online 14 February 2003
RID="a"
ID="a"e-mail: ccaizer@physics.uvt.ro 相似文献
20.
The interval of external magnetic fields where a mixed state can exist in a superconducting film with a fixed value of the
flux is determined. The equilibrium and reversible magnetization curves of the sample are calculated, and the dynamics of
the magnetic relaxation in the film is described. Nonuniform deformation of the Abrikosov lattice is predicted.
Pis’ma Zh. éksp. Teor. Fiz. 65, No. 5, 405–410 (10 March 1997) 相似文献