共查询到20条相似文献,搜索用时 15 毫秒
1.
L. A. Chebotkevich K. S. Ermakov A. V. Ognev E. V. Pustovalov 《Physics of the Solid State》2011,53(11):2266-2270
Arrays of circular nanodisks have been formed from epitaxial Co films deposited on atomically smooth and vicinal Si(111) single
crystals by using a focused Ga+ ion beam. The surface roughness has been determined by scanning tunneling microscopy. The coercive force and the processes
of magnetization reversal in films and arrays of epitaxial Co nanodisks have been studied. It has been shown that the coercive
force of the Co nanodisk arrays on the atomically smooth Si(111) surface is larger and that on the vicinal Si(111) surface
is smaller than that in the epitaxial films. The studies of the magnetic structure of the nanodisks by magnetic-force microscopy
in combination with the micromagnetic simulation have shown that the processes of magnetization reversal in the nanodisks
on the atomically smooth substrates occur through the vortex-like states and, on the vicinal substrates, through the C-type state. 相似文献
2.
A. A. Maximenko J. V. Kasiuk J. A. Fedotova M. Marszałek Y. Zabila J. Chojenka 《Physics of the Solid State》2017,59(9):1762-1770
We studied the structure and magnetic properties of porous multilayered Co/Pd films deposited on the templates of anodized Al2O3 with a specific surface morphology that is characterized by a cellular–porous structure with several pores inside each cell. X-ray diffraction analysis and reflectometry are used to study the peculiarities of the formation of phases in deposited films. The effect of morphological features of porous Co/Pd films on their magnetoanisotropic properties and magnetization reversal processes (magnetization reversal mechanisms, domain structure of films, and coercive field H c ) is revealed by SQUID magnetometry and magnetic force microscopy. 相似文献
3.
We have studied the effect of magnetic disorder on the magnetization reversal process in thin Co/CoO films. The antiferromagnetic CoO layer allows a reversible tuning of the magnetic disorder by simple temperature variation. For temperatures above a critical temperature T(c), we observe a discontinuous magnetization reversal, whereas smooth magnetization loops occur for T相似文献
4.
A. Adanlété AdjanohR. Belhi J. VogelM. Ayadi K. Abdelmoula 《Journal of magnetism and magnetic materials》2011,323(5):504-508
Magnetization reversal in ultra-thin Au/Co/Au films deposited on single crystal silicon (1 0 0) was investigated using Kerr microscopy. In the considered ultra-thin Co films, with a thickness between 0.7 and 1 nm, the coercivity and magnetic anisotropy decrease with decrease in cobalt layer thickness and the magnetization reversal dynamics is dominated by disordered domain wall motion. An analysis of the observed magnetization reversal dynamics is proposed, starting from the Fatuzzo-Labrune model. We show that the relaxation curves of these samples are well described by a function obtained by a technical transformation of Fatuzzo-Labrune model in the regime dominated by domain wall motion. 相似文献
5.
A. Adanlété Adjanoh J. Vogel M. Ayadi 《Journal of magnetism and magnetic materials》2010,322(17):2498-2504
We present a study of the magnetization reversal dynamics in ultrathin Au/Co/Au films with perpendicular magnetic anisotropy, for a Co thickness of 0.5, 0.7 and 1 nm. In these films, the magnetization reversal is dominated by domain nucleation for tCo=0.5, 0.7 nm and by domain wall propagation for tCo=1 nm. The prevalence of domain nucleation for the thickness range 0.5-0.7 nm is different from results reported in the literature, for the same system and for the same thickness range, where the magnetization reversal took place mainly by domain wall motion. We attribute this difference to the effect of roughness of the Au buffer layer on the morphology of the magnetic layer. 相似文献
6.
We have measured the spin-resolved photoemission spectra of the Co thin films grown epitaxially on Au(1 1 1) substrate in order to investigate their valence band structures. It is proved that the electronic structures of Co thin films are pretty different from that of bulk hcp-Co. It is observed that as the films grow thicker, the electronic structures become closer to those of the bulk Co with the magnetic anisotropy turning into in-plane magnetization from out-of-plane magnetization. 相似文献
7.
The influence of patterning on exchange bias has been
investigated using arrays of micron-sized Co/CoO dots with different lateral
confinement and length-to-width ratio. The patterned samples show higher
coercive and exchange bias fields than a continuous Co/CoO bilayer. As in
unpatterned film, magnetization reversal mechanisms on opposite sides of the
hysteresis loops of the microstructured samples are different. However, with
the increase of lateral confinement and shape anisotropy of the dots, the
asymmetry in the magnetization reversal starts to differ from that observed
in continuous Co/CoO films. 相似文献
8.
Effect of CoSi2 buffer layer on structure and magnetic properties of Co films grown on Si(001) substrate
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Buffer layer provides an opportunity to enhance the quality of ultrathin magnetic films.In this paper,Co films with different thickness of Co Si2buffer layers were grown on Si(001)substrates.In order to investigate morphology,structure,and magnetic properties of films,scanning tunneling microscope(STM),low energy electron diffraction(LEED),high resolution transmission electron microscopy(HRTEM),and surface magneto-optical Kerr effect(SMOKE)were used.The results show that the crystal quality and magnetic anisotropies of the Co films are strongly affected by the thickness of Co Si2buffer layers.Few Co Si2monolayers can prevent the interdiffusion of Si substrate and Co film and enhance the Co film quality.Furthermore,the in-plane magnetic anisotropy of Co film with optimal buffer layer shows four-fold symmetry and exhibits the two-jumps of magnetization reversal process,which is the typical phenomenon in cubic(001)films. 相似文献
9.
Iunin YL Kabanov YP Nikitenko VI Cheng XM Clarke D Tretiakov OA Tchernyshyov O Shapiro AJ Shull RD Chien CL 《Physical review letters》2007,98(11):117204
We report unexpected phenomena during magnetization reversal in ultrathin Co films and Co/Pt multilayers with perpendicular anisotropy. Using magneto-optical Kerr microscopy and magnetic force microscopy we have observed asymmetrical nucleation centers where the reversal begins for one direction of the field only and is characterized by an acute asymmetry of domain-wall mobility. We have also observed magnetic domains with a continuously varying average magnetization, which can be explained in terms of the coexistence of three magnetic phases: up, down, and striped. 相似文献
10.
Zhao HB Talbayev D Lüpke G Hanbicki AT Li CH van't Erve MJ Kioseoglou G Jonker BT 《Physical review letters》2005,95(13):137202
The reversal process of the Fe interface layer magnetization in Fe/AlGaAs heterostructures is measured directly using magnetization-induced second-harmonic generation, and is compared with the reversal of the bulk magnetization as obtained from magneto-optic Kerr effect. The switching characteristics are distinctly different due to interface-derived anisotropy--single step switching occurs at the interface layer, while two-jump switching occurs in the bulk Fe for the magnetic field orientations employed. The angle between the interface and bulk magnetization may be as large as 40-85 degrees. Such interface switching will dominate the behavior of nanoscale structures. 相似文献
11.
The domain structure in strained garnet ferrite films and its behavior in an external magnetic field are studied using the Faraday effect. Based on the experimental results, a model of magnetization reversal in thin polycrystalline layers is proposed that describes the process of remagnetization as the development of fractal clusters. The model proposed is verified using a computer simulation of magnetization reversal. 相似文献
12.
M. Hossain G. Bergmann 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(1):7-11
Thin quench-condensed films of Rb and K are covered with 1/100 of a mono-layer of Fe or Co. Then the impurities are covered
with several atomic layers of the host. The magnetization of the films is measured by means of the anomalous Hall effect (AHE).
The magnetization follows a Brillouin function with a magnetic moment of more than 10 Bohr magnetons for bulk Co and Fe impurities.
These moments are much larger than the moments of the atomic configurations of Fe and Co and suggest enhanced magnetic moments
of the impurities.
Received 22 September 2001 and Received in final form 11 December 2001 相似文献
13.
O. Peña M. Guilloux-Viry Wei Peng Yanwei Ma C. Moure 《Journal of magnetism and magnetic materials》2009,321(11):1723-1726
We present herein a comparison of the magnetic properties of bulk ceramics and thin films of the ferrimagnetic ErCo0.50Mn0.50O3 compound. Epitaxial thin films were deposited onto (1 0 0) SrTiO3 substrates by pulsed-laser ablation while bulk ceramics were prepared by solid state reaction. When cooling under low applied fields, a spin reversal is observed in both thin film and bulk due to the competition between two magnetic sublattices (Co/Mn and Er) coupled by a negative exchange interaction. Original features are observed in the M(H) loops for bulk materials: abrupt jumps at 4 T due to a reorientation of domains, while in the low field region, the increasing and decreasing branches of the magnetization intersect each other. In the thin film, the ordering temperature increased from 69 to 75 K, and the ZFC anomaly (AF transition) became sharper, compared to the bulk specimen. The oxygen content and the microstructure are crucial to observe the intersection of the magnetization branches. 相似文献
14.
We report on properties of layered coherent structures of Pd and Co, prepared by RF sputtering. X-ray diffraction analysis characterizes these films as having a well-ordered periodic structure (periods λ in the range 10A < λ < 80A) of stacked (111) planes of fcc Co and Pd. Room temperature magnetic properties were measured with a vibrating sample magnetometer. All films are ferromagnetic, with a magnetic moment in excess of that attributable to Co. This excess, which increases as λ decreases, is interpreted as induced ferromagnetism in the Pd layers. The in-plane magnetization is harder for smaller values of λ and appears to depend mainly on the thickness of the Co layers. The in-plane electrical resistivity was measured in the range 2K–300K by a four-electrode method. Below 40K, the resistivity is dominated by residual resistivity; above this temperature, its rise is attributed mainly to the resistivities of bulk Pd and Co. The λ-dependence of the resistivity is described by a model of interfacial scattering of electrons. Evidence for the presence of coherency strains at small λ is present in the x-ray data, the magnetization behavior, as well as in the interfacial scattering mechanism deduced from the analysis of the resistivity. 相似文献
15.
Ulbrich TC Makarov D Hu G Guhr IL Suess D Schrefl T Albrecht M 《Physical review letters》2006,96(7):077202
The deposition of Co/Pd multilayer films onto self-assembled particle arrays with particle sizes down to 50 nm leads to pronounced curvature-induced physical properties. Unlike in classical nanosystems, the so-formed single caps on top of the spherical particles exhibit a radial symmetric anisotropy orientation across their surface. Its impact on the magnetization reversal process was analyzed experimentally for different particle sizes and compared to micromagnetic simulations, offering new opportunities in the functionalization of magnetic nanostructures. 相似文献
16.
R. Krishnan 《Journal of magnetism and magnetic materials》1985,50(2):189-192
Compositionally modulated (CM) films of Co-Nb have been prepared by sequential evaporation onto Si substrates using two E-guns fitted in an UHV system. The thickness of the Co sublayer was varied in the range 50 to 105 Å and that of Nb in the range 18 to 90 Å. A single layer Co film of about 850 Å was also prepared and studied. Magnetization was measured using a VSM at 290 K. FMR was observed at about 9.8 GHz in the range 3 to 290 K. For Co a layer thickness of 50 Å the magnetization in CM film is about 12% lower at 4.2 K, as compared to the bulk value. The FMR spectrum of single layer Co film shows a single absorption in the perpendicular configuration with a narrow line width of 40 Oe. Other properties of this film agree with those published in the literature. In CM films, multiple absorption modes are observed. A small perpendicular anisoropy is also measured. The magnetization in all the samples varies at T3/2. The Curie temperature of CM films is lower than that of bulk Co. The resonance line width in CM films at lower temperatures, increases much faster than in Co film. 相似文献
17.
A. A. Timopheev S. M. Ryabchenko V. M. Kalita A. F. Lozenko P. A. Trotsenko O. V. Stognei A. V. Sitnikov 《Physics of the Solid State》2011,53(3):494-503
This paper reports on the results of the magnetostatic measurements for Co-Al-O nanogranular films over a wide range of concentrations
of the ferromagnetic component x. It has been revealed that grains in the films are characterized by the growth-induced anisotropy with easy axes directed
perpendicular to the film plane. The maximum field of the single-grain perpendicular anisotropy reaches ∼2.5 kOe for samples
in the vicinity of the percolation threshold (x ≈ 61 at % Co). It has been established that the characteristic features of the superparamagnetic behavior of an ensemble
of oriented Stoner-Wohlfarth particles are retained for the sample with x ≈ 61 at % Co in the presence of the demagnetization field associated with the net magnetization of the film. The influence
of the demagnetization field of the film on the shape of the magnetization reversal curves, the coercivity, and the blocking
temperature has been investigated and simulated. The results of the simulation are consistent with the experimental data. 相似文献
18.
In this paper, the magnetization reversal of the ferromagnetic
layers in the IrMn/CoFe/AlOx/CoFe magnetic tunnel junction has
been investigated using bulk magnetometry. The films exhibit very
complex magnetization processes and reversal mechanism. Thermal
activation phenomena such as the training effect, the asymmetry of
reversal, the loop broadening and the decrease of exchange field
while holding the film at negative saturation have been observed on
the hysteresis loops of the pinned ferromagnetic layer while not on
those of the free ferromagnetic layer. The thermal activation
phenomena observed can be explained by the model of two energy
barrier distributions with different time constants. 相似文献
19.
It is found that the magnetization reversal of an array of superthin Co films coupled by the ferromagnetic exchange interaction through the Ag layers may result in a domain structure of an unexpected new type. Due to the incoherent different-sense spin rotation upon lowering the field perpendicular to the easy axis, the specific macrodomains first form in a sample. They are separated not by the Neél domain wall but by a wide transition region containing high-density microdomains of sizes correlating with the grain sizes in the films. Further magnetization reversal proceeds through the formation of standard domain walls in the macrodomain in a magnetostatic field at the plate edge and through their shifting toward the transition region. These processes are explained with taking into account the character of the revealed magnetic anisotropy dispersion. 相似文献
20.
We investigate the magnetization reversal of individual Co islands on Cu(111) in the size range of N=700 to 18,000 atoms by spin-polarized scanning tunneling microscopy at 8 K. The switching field H(sw) changes with island size in a nonmonotonic manner: it increases with island size and reaches a maximum value of 2.4 T at N=5500 atoms, and it decreases for larger islands. We extract the energy barrier for magnetization reversal as a function of island size. The maximum H(sw) corresponds to an energy barrier of 1 eV. Our results elucidate a crossover of the magnetization reversal from an exchange-spring behavior to domain wall formation with increasing size at around 7500 atoms. 相似文献