共查询到20条相似文献,搜索用时 656 毫秒
1.
V. L. Mironov A. A. Fraerman B. A. Gribkov O. L. Ermolaeva S. A. Gusev S. N. Vdovichev 《Physics of the Solid State》2010,52(11):2297-2302
The processes of local magnetization reversal of elliptic Co/Si/Co nanodisks under the action of a nonuniform magnetic field
of a magnetic-force microscope (MFM) probe have been investigated. The specific features of the distribution of the phase
MFM contrast from particles with ferromagnetic and antiferromagnetic configurations of the magnetic moments in neighboring
Co layers have been discussed. It has been shown experimentally that, under the action of the probe field, there occur orientational
transitions of two types: transitions from the ferromagnetic configuration to the antiferromagnetic configuration due to the
reorientation of the magnetization of the upper layer and transitions in the antiferromagnetic configuration with a change
in the orientation of the magnetic moment in both ferromagnetic layers. The presented results of micromagnetic simulation
of the processes of transformation of the magnetization in such particles under the action of the MFM probe field explain
the main regularities of the magnetization reversal processes. 相似文献
2.
V.L. Mironov B.A. GribkovA.A. Fraerman S.A. GusevS.N. Vdovichev I.R. KaretnikovaI.M. Nefedov I.A. Shereshevsky 《Journal of magnetism and magnetic materials》2007
Magnetic force microscopy (MFM) methods were applied to investigate the peculiarities of magnetization distribution in elliptical 400×600×27 nm Co particles. Reversible transitions between the uniform and vortex states under inhomogeneous magnetic field of MFM probe were observed. Possibility to control the chirality of a magnetic vortex in these particles by MFM probe manipulation was shown. 相似文献
3.
V. S. Gornakov Yu. P. Kabanov V. I. Nikitenko O. A. Tikhomirov A. J. Shapiro R. D. Shull 《Journal of Experimental and Theoretical Physics》2004,99(3):602-612
Distribution of a magnetic moment in an exchange-coupled bilayer Fe/SmCo epitaxial structure grown on a (110) MgO substrate is visualized by the magnetooptic indicator film technique. The direction and the magnitude of the effective magnetization in this structure are determined both under external magnetic fields of variable magnitude and direction and after the removal of these fields. It is shown that such a heterostructure is remagnetized by a nonuniform rotation of a magnetic moment both along the thickness of a sample and in its plane. A field antiparallel to the axis of unidirectional anisotropy gives rise to spin springs with opposite chiralities in different regions of the magnetically soft ferromagnetic layer. The contributions of these springs to the net magnetization cancel out, thus decreasing the averaged magnetic moment and the remanent magnetization without their rotation. When the external field deviates from the easy axis, the balance is violated and the sample exhibits a quasi-uniform rotation of the magnetic moment. Asymmetry in the rotation of the magnetic moment is observed under the reversal of the field as well as under repeated remagnetization cycles. It is established that a monochiral spin spring is also formed in a rotating in-plane magnetic field when the magnitude of the field exceeds the critical value. Possible mechanisms of remagnetization in this system are discussed with regard to the original disordered orientation of magnetization of the magnetically soft layer with respect to the easy axis, which is defined by the variance of unidirectional anisotropy axes of this layer on the interface. 相似文献
4.
A. D. Talantsev O. V. Koplak G. L. L’vova O. S. Dmitriev S. Petit Watelot Y. Lu S. Mangin R. B. Morgunov 《Physics of the Solid State》2017,59(10):1947-1951
Negative magnetoresistance modifying the quality factor of a microwave cavity under the magnetization switching of ferromagnetic layers has been discovered in a MgO/CoFeB/MgO/Ta film with a single ferromagnetic layer and a MgO/CoFeB/Ta/CoFeB/MgO/Ta spin valve consisting of two ferromagnetic CoFeB layers. The dependence of the first derivative dP/dH of the microwave absorption signal on the dc magnetic field of the spectrometer exactly reproduce the magnetic hysteresis loops of the sample. The slope of these dependences and the amplitude of dP/dH jumps under remagnetization of the layers are determined by the interplay of a negative magnetoresistance of individual layers and a positive giant magnetoresistance of the entire multilayer structure. The discovered phenomenon allows using microwave absorption for making a high-sensitivity contact-free indicator of the basic magnetization states of a spin valve. 相似文献
5.
N. Morales Mendoza S. Goyanes C. Chiliotte V. Bekeris G. Rubiolo R. Candal 《Physica B: Condensed Matter》2012,407(16):3203-3205
Magnetic binary nanofillers containing multiwall carbon nanotubes (MWCNT) and hercynite were synthesized by Chemical Vapor Deposition (CVD) on Fe/AlOOH prepared by the sol–gel method. The catalyst precursor was fired at 450 °C, ground and sifted through different meshes. Two powders were obtained with different particle sizes: sample A (50–75 μm) and sample B (smaller than 50 μm). These powders are composed of iron oxide particles widely dispersed in the non-crystalline matrix of aluminum oxide and they are not ferromagnetic. After reduction process the powders are composed of α-Fe nanoparticles inside hercynite matrix. These nanofillers are composed of hercynite containing α-Fe nanoparticles and MWCNT. The binary magnetic nanofillers were slightly ferromagnetic. The saturation magnetization of the nanofillers depended on the powder particle size. The nanofiller obtained from powder particles in the range 50–75 μm showed a saturation magnetization 36% higher than the one formed from powder particles smaller than 50 μm. The phenomenon is explained in terms of changes in the magnetic environment of the particles as consequence of the presence of MWCNT. 相似文献
6.
Fritzsche J Moshchalkov VV Eitel H Koelle D Kleiner R Szymczak R 《Physical review letters》2006,96(24):247003
Nanoscale magnetic and superconducting properties of the superconductor-ferromagnet Nb/PbFe12O19 hybrid were studied as a function of applied magnetic fields. Low-temperature scanning laser microscopy (LTSLM) together with transport measurements were carried out in order to reveal local variations of superconductivity induced by the magnetic field template produced by the ferromagnetic substrate. Room temperature magnetic force microscopy (MFM) was performed and magnetization curves were taken at room and low temperature to investigate the magnetic properties of the hybrid. Comparative analysis of the LTSLM and the MFM images has convincingly demonstrated the presence of the reverse-domain superconductivity. 相似文献
7.
N. A. Djuzhev A. M. Kozmin M. Yu. Chinenkov 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2016,10(1):39-42
The results of studying regions of inhomogeneous magnetization on the surface of permalloy thin films with the use of fabricated highly sensitive probes of magnetic force microscopy (MFM) are presented. The technological features of manufacturing MFM probes with a high sensitivity to magnetic-field gradient are analyzed. Regions of ordering of the vertical component of the magnetic field are revealed, and domain walls are visualized in the thin films under study. Nanoscale measurements of the domain-wall thicknesses are performed. 相似文献
8.
P. Granitzer K. Rumpf A.G. Roca M.P. Morales P. Poelt M. Albu 《Journal of magnetism and magnetic materials》2010,322(9-12):1343-1346
Magnetite nanoparticles, which are coated with oleic acid in a hexane solution and exhibit an average diameter of 7.7 nm, were embedded in a porous silicon (PS) matrix by immersion under defined parameters (e.g. concentration, temperature, time). The porous silicon matrix is prepared by anodization of a highly n-doped silicon wafer in an aqueous HF-solution. Magnetic characterization of the samples has been performed by SQUID-magnetometry. The superparamagnetic behaviour of the magnetite nanoparticles is represented by temperature-dependent magnetization measurements. Zero field (ZFC)/field cooled (FC) experiments indicate magnetic interactions between the particles. For the infiltration into the PS-templates different concentrations of the magnetite nanoparticles are used and magnetization measurements are performed in respect with magnetic interactions between the particles. The achieved porous silicon/magnetite specimens are not only interesting due to their transition between superparamagnetic and ferromagnetic behaviour, and thus for magnetic applications but also because of the non-toxicity of both materials giving the opportunity to employ the system in medical applications as drug delivery or in medical diagnostics. 相似文献
9.
V. L. Mironov O. L. Yermolaeva 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2007,1(4):466-470
The interaction of a magnetic vortex in a circular ferromagnetic nanoparticle with the probe field of a magnetic force microscope (MFM) is theoretically investigated. In the calculations, the probe field is approximated by the point dipole field. The rigid magnetic vortex model is used to describe the vortex state of magnetization. It is found that the effect of the probe field on the rigid magnetic vortex shell is similar to the effect of a uniform magnetic field parallel to the particle plane. The effect of the Z component of the probe field on the core of the vortex results in mutual probe-vortex attraction or repulsion. It is shown that the magnetization direction of the core of the vortex in the MFM probe field can be changed without a change in the shell vorticity direction. 相似文献
10.
N. V. Vorob’eva A. N. Lachinov F. F. Garifullina 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(10):1357-1359
The association between the threshold value of conductance switching in an external magnetic field and the initial magnetic state of a ferromagnetic plate substrate is shown for a ferromagnet/polymer/nonmagnetic metal system. The threshold magnetic field change is explained by appearance of residual magnetization after being held in an external magnetic field and, correspondingly, by the change in the initial state upon further remagnetization. 相似文献
11.
D. O. Filatov E. I. Malysheva 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2007,1(3):352-358
The dependence of magnetic properties of GaAs:Mn and MnAs epitaxial films grown on GaAs (001) by laser ablation of Mn and undoped GaAs in a hydrogen atmosphere under the growth conditions has been studied by magnetic force microscopy (MFM). Magnetic probe calibration for quantitative MFM measurements was performed by scanning across the slit of the magnetic-head of a tape recorder through which controlled direct current was passed. The dipole approximation was used to describe the magnetic properties of the MFM probe. Nonuniformity of the magnetization of GaAs:Mn films related to the formation of MnAs nanoinclusions, which are ferromagnetic at 300 K, has been observed. The typical scales of the spatial nonuniformity of the magnetization of GaAs:Mn films were varied from 270 to 550 nm depending on the film-growth conditions. The MnAs phase was identified by MFM measurements at an elevated temperature (up to 80°N). 相似文献
12.
K. Rivkin I.P Nevirkovets J.B. Ketterson B.K. Sarma 《Journal of magnetism and magnetic materials》2009,321(19):3324-3329
A number of studies have shown that ferromagnetic resonance linewidths in magnetic thin films contain a significant contribution due to processes, such as inhomogeneous broadening and two-magnon scattering followed by decay to the phonon thermal bath. We present a classical theoretical approach that permits the calculation of such processes for arrays of arbitrarily shaped magnetic nanoparticles and, by comparison with experimental results, demonstrates that the linewidth broadening and damping are dominated by inhomogenities that strongly depend on the equilibrium state of magnetization and can be used to identify the latter. 相似文献
13.
Sunil K. Mishra 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,78(1):65-73
We investigate slow dynamics of collection of a few noninteracting
antiferromagnetic NiO nanoparticles.
Our purpose is to enquire the role of size-dependent magnetization
fluctuations in temperature and time dependent properties of
antiferromagnetic nanoparticles. The zero-field cooled magnetization
exhibits size dependent fluctuations. We find memory effects in
field cooled magnetization, as well as aging effects in
thermoremenant magnetization of antiferromagnetic nanoparticles.
The antiferromagnetic nanoparticles show a stronger memory effect
than the corresponding effect in the ferromagnetic particles, when
the distribution of particles include very small sizes.
The situation reverses for bigger sizes. The relaxation of
the magnetization after a sudden cooling, heating and removal
of fields reiterate the memory effects. We also see a weak signature
of size-dependent magnetization fluctuations in aging effect of
antiferromagnetic nanoparticles. We find a two-step relaxation of
thermoremenant magnetization in antiferromagnetic case, which
differs qualitatively from relaxation of ferromagnetic nanoparticles. 相似文献
14.
《中国物理 B》2019,(7)
The local detection of magnetic domains of isolated 10 nm Fe_3O_4 magnetic nanoparticles(MNPs) has been achieved by field-variable magnetic force microscopy(MFM) with high spatial resolution.The domain configuration of an individual MNP shows a typical dipolar response.The magnetization reversal of MNP domains is governed by a coherent rotation mechanism, which is consistent with the theoretical results given by micromagnetic calculations.Present results suggest that the field-variable MFM has great potential in providing nanoscale magnetic information on magnetic nanostructures,such as nanoparticles, nanodots, skyrmions, and vortices, with high spatial resolution.This is crucial for the development and application of magnetic nanostructures and devices. 相似文献
15.
B. Yu. Sokolov 《Physics of the Solid State》2005,47(2):263-266
The magnetic linear birefringence of an FeBO3: Mg ferromagnetic crystal is investigated as a function of the magnetic field strength, the magnetic field orientation, and the coordinates. The structure of the inhomogeneous magnetic phase of this weak ferromagnet is determined by analyzing the experimental results obtained. It is shown that, in an inhomogeneous magnetic state, the ferromagnetic moment does not deviate from the basal plane of the crystal and the angle of its deviation from the direction of the applied magnetic field is described by a one-dimensional harmonic function of the spatial coordinate along the axis of magnetization. 相似文献
16.
V. L. Mironov D. S. Nikitushkin D. S. Petrov A. B. Shubin P. A. Zhdan 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2007,1(3):348-351
Calculations of the magnetic force microscopy (MFM) contrast from low-coercive ferromagnetic and superparamagnetic particles are presented. It is shown that the external field stabilizes the magnetic moment of particles, allowing the separation of contributions of van der Waals and magnetic interactions to the MFM phase contrast. The values of stabilizing magnetic fields are estimated. 相似文献
17.
V. V. Uglov V. M. Astashynski N. T. Kvasov I. L. Doroshevich 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2014,8(4):821-827
The results of research into the behavior of the magnetic structure inherent to spherical ferromagnetic nanoparticles with radii of 5–30 nm are presented. The behavioral features are investigated in an external magnetic field by means of computer modeling. The hysteresis loops and formation of the vortex structure of magnetization are analyzed using particles with different sizes. The size effect of changes in the magnetization symmetry, which is analogous to phase transitions of the second kind, is established. The magnetic moments of spherical iron nanoparticles with radii of 5–30 nm are calculated. Calculations are performed by means of the Nmag micromagnetic simulation package. 相似文献
18.
Magnetization relaxation of uniaxial anisotropic ferromagnetic particles with linear reaction dynamics driven by DC/AC magnetic field 下载免费PDF全文
《中国物理 B》2021,30(9):90202-090202
The response of uniaxial anisotropic ferromagnetic particles with linear reaction dynamics subjected to alternating current(AC) or direct current(DC) bias magnetic field is evaluated by the reaction–diffusion equation for the probability distribution function of the molecular concentration in the spherical coordinate system. The magnetization function and the probability distribution function of the magnetic particles in the reaction system are derived by using the Legendre polynomials and Laplace transform. We discuss the characteristics of magnetization and probability distribution of the magnetic particles with different anisotropic parameters driven by a DC and AC magnetic fields, respectively. It is shown that both the magnetization and the probability distribution decrease with time increasing due to the reaction process. The uniformity of the probability distribution and the amplitude of the magnetization are both affected by the anisotropic parameters.Meanwhile, the difference between the case with linear reaction dynamics and the non-reaction case is discussed. 相似文献
19.
20.
V. Markovich G. Jung A. Wisniewski D. Mogilyansky R. Puzniak A. Kohn X. D. Wu K. Suzuki G. Gorodetsky 《Journal of nanoparticle research》2012,14(9):1-18
Magnetic properties of electron-doped La0.23Ca0.77MnO3 manganite nanoparticles, with average size of 12 and 60?nm, prepared by the glycine?Cnitrate method, have been investigated in the temperature range 5?C300?K and magnetic fields up to 90?kOe. It is suggested that weak ferromagnetic moment results from ferromagnetic shells of the basically antiferromagnetic nanoparticles and from domains of frustrated disordered phase in the core. Assumption of two distinct sources of ferromagnetism is supported by the appearance of two independent ferromagnetic contributions in the fit of the T 3/2 Bloch law to spontaneous magnetization. The ferromagnetic components, which are more pronounced in smaller particles, occupy only a small fraction of the nanoparticle volume and the antiferromagnetic ground state remains stable. It is found that the magnetic hysteresis loops following field cooled processes, display size-dependent horizontal and vertical shifts, namely, exhibiting exchange bias effect. Time-dependent magnetization dynamics demonstrating two relaxation rates were observed at constant magnetic fields upon cooling to T?<?100?K. 相似文献