共查询到18条相似文献,搜索用时 15 毫秒
1.
Laser-induced ultrafast magnetization dynamics and transient coercivity behavior in perpendicular magnetized L10-FePt films are investigated using the time-resolved polar magneto-optical Kerr technique. The magnetization after photo-excitation shows a dramatic reduction on the picosecond time scale. In contrast, the coercivity shows a weak decrease, accompanied by a skewed Kerr loop shape for low and intermediate fluences. The results can be interpreted by the laser-induced non-uniform demagnetization due to the weakened coupling between FePt grains of different size and/or components. The remaining coercivity vanishes when the film is fully demagnetized at higher fluence. We claim that the remaining coercivity can be manipulated by employing appropriate laser energy and film thickness, which may be helpful for application in heat-assisted magnetic recording. 相似文献
2.
A series of L10 Fe63Pt37 films with controlled thickness (tFM) were deposited on MgO(100) substrates for microstructure and magnetization reversal mechanism study. X-ray diffraction measurements show that face-centered tetragonal (200) peak also exists in addition to face-centered tetragonal (002) one, and becomes weak for thick films. High resolution electron microscopy study reveals the existence of periodic misfit dislocations at the FePt/MgO interface and other types of defects such as twins and antiphase boundary inside the film. Out-of-plane initial magnetization shows a slow increase responding to the external magnetic field and then follows a steep increase. The out-of-plane coercivity HC at room temperature decreases with increasing tFM and increases when the angle θH between the external magnetic field and the film normal direction increases. HC at θH = 0 changes as a linear function of temperature for individual samples and the slope decreases with increasing tFM. In addition, magnetic viscosity measurements show that the fluctuation field at room temperature decreases with increasing tFM. These phenomena indicate that the magnetization reversal in the L10 FePt films should be realized by the motion of weakly pinned domain wall and thus governed by the thermal activation model. The magnetization reversal thermal activation volume and corresponding energy increase with increasing tFM, as a result of the interactions between domain walls and structural defects can be attributed to the sample microstructural characteristic evolution with tFM. 相似文献
3.
We studied the effects of MgO and MgO/Pd seed-layers on perpendicular magnetic anisotropy in co-sputtered CoPd films. CoPd films with the MgO seed-layer showed perpendicular magnetic properties that were superior to those with another after annealing. The loop squareness was unity, indicating strong perpendicular magnetic anisotropy, when the MgO seed-layer was thicker than 2 nm. We observed that the out-of-plane CoPd (111) texture was strongly developed, as well as the in-plane tensile stress in the CoPd films. The magnetoelastic anisotropy coming from a negative magnetostriction λ111 under the in-plane tensile stress dominating over other anisotropies is likely responsible for creating such strong perpendicular magnetic anisotropy. In the case of the MgO/Pd seed-layer, the CoPd films showed mixed anisotropy having both in-plane and out-of-plane magnetic anisotropy components after annealing. The appearance of the strong (100) texture of the CoPd films with the MgO/Pd seed-layer is believed to have caused the decrease in the perpendicular magnetic anisotropy that originated from the magnetoelastic anisotropy due to the additional contribution from the positive magnetostriction λ100 but less contribution from the negative magnetostriction λ111 when the CoPd films are under in-plane tensile stress. 相似文献
4.
Pseudobinary SmCo7 − xCux intermetallic compound films with a TbCu7-type structure were prepared by sputtered (SmCo7/Cu)n multilayer. After annealing, the spacer layer Cu (0.5-1.5 nm) diffused into the SmCo7 matrix and stabilized the SmCo7 meta-stable phase. The resulting microstructure was investigated by transmission electron microscopy. Perpendicular anisotropy was obtained by introducing a Cu/Ti dual underlayer during sputtering, resulting in prefer-orientated SmCo7 (00L) X-ray diffraction peaks. This study observes a maze-like domain pattern in perpendicular anisotropy films and finds single- and multi-domain particles in correlated AFM and MFM images. 相似文献
5.
The FePt films with various thicknesses (t) of 5 to 50 nm are deposited on Si(100) substrate without any underlayer by in-situ annealing at substrate temperature (Ts) of 620 °C. A strong (001) texture of L10 FePt film is obtained and presents high perpendicular magnetic anisotropy as the film thickness increases to 30 nm. By further increasing the thickness to exceed 30 nm, the (111) orientation of L10 FePt is enhanced greatly, indicating that the quality of perpendicular magnetic anisotropy degrades when the thickness of the FePt film is greater than 30 nm. The single-layered FePt film with thickness of 30 nm by in-situ depositing at 620 °C shows good perpendicular magnetic properties (perpendicular coercivity of 1033 kA/m (13 kOe), saturation magnetization of 1.08 webers/m2 and perpendicular squareness of 0.91, respectively), which reveal its significant potential for perpendicular magnetic recording media. 相似文献
6.
F. ZhangF.S. Wen L. LiN. Wang X.Y. HanY.F. Lu Z.Y. Liu B. XuD.L. Yu J.L. HeY.J. Tian 《Thin solid films》2011,519(16):5596-5599
The effect of an ultra thin NiO(11 Å) capping layer on the temperature dependence of the interlayer coupling of a [Pt(26.5 Å)/Co(4 Å)]3 multilayer with perpendicular anisotropy has been investigated. In the presence of the NiO(11 Å) capping layer, the interlayer coupling between the Co layers has been observed to demonstrate interesting temperature-dependent transitions. Only the antiferromagnetic (AF) interlayer coupling exists at T ≥ 270 K. With the decrease of temperature, the coexistence of ferromagnetic (FM) and antiferromagnetic interlayer coupling is observed in the temperature range of 220 K ≤ T≤ 270 K. When the temperature is lower than 220 K, only the ferromagnetic interlayer coupling exists. The temperature-dependent polarization of the Pt layers can be one of the origins for the observed AF-to-FM transitions. 相似文献
7.
Zn0.91Al0.07Ni0.02O and Zn0.90Al0.05Ni0.05O films of about 250 nm thick were deposited on glass substrates at 300 K by co-sputtering with ZnO:Al and Ni targets. The films were annealed in vacuum at 673 K for 2 h and then cooled down to room temperature under a magnetic field of 4.8 × 104 A m−1 applied along the film plane. After this process the films showed room temperature ferromagnetism, a resistivity of about 2 × 10−3 Ω cm and an average transmittance of 75% in the visible wavelength range. The films have a wurtzite structure with the c-axis orientation in the film growing direction and consist of thin columnar grains perpendicular to the substrate. A temperature dependence of the resistivity from 2 K to 300 K reveals that the carrier transport mechanism is thermally activated band conduction above 150 K and Mott's variable range hopping below 70 K. 相似文献
8.
Most nickel (Ni) films galvanostatically electrodeposited at 40-50 °C exhibited low hardness about 4 GPa and rough surface. In this article, we have investigated Ni electrodeposition at low temperatures of 5-20 °C in order to enhance the hardness and smoothness of films and performed by potentiostatic mode instead of galvanostatic mode to avoid the low-temperature precipitation of electrolyte agents. Effect of temperature on the evolution of diffusion coefficient, deposition rate, morphology and hardness was studied. Electrodeposition at low temperature without hard-element addition can reduce diffusion rate and produce the fine-grain, smooth morphology and dense film together with compressive residual stress to enhance hardness up to 6.18 GPa at 5 °C. The growth and hardening mechanism of low-temperature electrodeposited Ni were further discussed in details. 相似文献
9.
The collective properties of dislocations in MgO are investigated in the high temperature regime and at constant strain rate with 3D Dislocation Dynamics simulations. Intersections between slip systems 1/2〈1 1 0〉{1 1 0} and 1/2〈1 1 0〉{1 0 0} allow essentially two types of junction reactions. These junctions are energetically stable and are expected to promote strong forest strengthening at high temperature. Large-scale DD simulations show that MgO strain hardening at high temperature may be dominated by forest reactions. Important parameters for dislocation density based modeling of MgO plasticity are finally calculated and verified to be consistent with experimental observations. 相似文献
10.
LaNiO3 (LNO) thin films were deposited by radio frequency magnetron sputtering on n-type Si (100) wafers at room temperature (RT). The as-sputtered LNO thin films were amorphous and had very high RT electrical resistivity even after post-annealing at 800 °C. The amorphous as-sputtered LNO films could be transformed to polycrystalline LNO films in rhombohedral phase by heating at 400 °C in an O2 atmosphere at pressure ranging from 1.5 to 8.0 MPa. Very low RT resistivity of LNO films were obtained by this high oxygen-pressure processing. The lowest value was as low as 1.09 × 10− 4 Ω cm by processing at oxygen pressure of 8 MPa. Such preparation of LNO thin films is compatible with the Si-based readout integrated circuits. Highly (100)-oriented perovskite structure of Pb(Zr0.52Ti0.48)O3 thin films was formed on this rhombohedral phase LNO, and good ferroelectricity could also be obtained on these HOPP-processed rhombohedral phase LNO films. 相似文献
11.
The development of Arctic oil and gas fields requires low temperature high strength steel materials that can resist critical loads in extreme environments. This paper investigates the mechanical properties such as stress–strain curves, elastic modulus, yield strength, ultimate tensile strength, and fracture strain of normal mild steel and high strength S690 steel to be used in low temperatures relevant to arctic environment. Tensile tests are carried out on steel coupons at different temperatures ranging from −80 °C to +30 °C in a cooling chamber. The influences of the low temperatures on the mechanical properties of mild steel and high strength steel are compared and their differences are discussed. Regression analyses are also carried out on the test data to develop empirical formulae to predict the elastic modulus, yield strength, and ultimate strength of the steels at ambient low temperatures. Finally, design formulae are recommended and their accuracies are further confirmed by the test data including those from the literature. 相似文献
12.
L. L. Makarshin D. V. Andreev V. N. Parmon O. M. Tukhto 《Materials Research Innovations》2000,4(1):27-31
By measuring the imaginary part of the magnetic susceptibility of a GdBa2Cu3O7-x film, we found the effect of N2, O2 and Ar molecules low temperature adsorption on the superconducting properties of the film. The low temperature adsorption
of the gases affects the critical transport current and the transition temperature. In all cases, the transition region broadens,
as the degree of coverage of the film with the gas molecules increases. By processing the experimental data, we found the
critical current either growing linearly (for argon and nitrogen) or decreasing exponentially (for oxygen) with increasing
surface coverage by the adsorbed gas molecules.
Received: 27 June 2000 / Reviewed and accepted: 28 June 2000 相似文献
13.
Yun An Agnieszka Kuc Petko Petkov Marcelo Lozada‐Hidalgo Thomas Heine 《Small (Weinheim an der Bergstrasse, Germany)》2019,15(43)
Recent experiments have demonstrated transport and separation of hydrogen isotopes through the van der Waals gap in hexagonal boron nitride and molybdenum disulfide bulk layered materials. However, the experiments cannot distinguish if the transported particles are protons (H+) or protium (H) atoms. Here, reported are the theoretical studies, which indicate that protium atoms, rather than protons, are transported through the gap. First‐principles calculations combined with well‐tempered metadynamics simulations at finite temperature reveal that for h‐BN and MoS2, the diffusion mechanism of both protons and protium (H) atoms involves a hopping process between adjacent layers. This process is assisted by low‐energy phonon shear modes. The extracted diffusion coefficient of protium matches the experiment, while for protons it is several orders of magnitude smaller. This indicates that protium atoms are responsible for the experimental observations. These results allow for a comprehensive interpretation of experimental results on the transport of hydrogen isotopes through van der Waals gaps and can help identify other materials for hydrogen isotope separation applications. 相似文献
14.
We demonstrate the deposition of fully dense, stoichiometric TiN films on amorphous SiO2 by reactive high power impulse magnetron sputtering (HiPIMS) in the absence of both substrate heating and applied bias. Contrary to the highly underdense layers obtained by reactive dc magnetron sputtering (dcMS) under similar conditions, the film nanostructure exhibits neither intra- nor intergrain porosity, exhibiting a strong 111 preferred orientation with flat surfaces. Competitive grain growth occurs only during the early stages of deposition (< 100 nm). The strong differences in the kinetically-limited nanostructural evolution for HiPIMS vs. dcMS are explained by high real-time deposition rates with long relaxation times, high ionization probabilities for Ti, and broad ion energy distributions. 相似文献
15.
针对高温高尘环境中气体和灰分取样所面临的取样管融化烧断问题、堵塞问题和卤化碱凝结问题,提出一种实验用髙温高尘气体灰分同时取样装置。该装置由取样探头和过滤取样器两部分组成,其中采用三层水冷套管的取样探头解决取样管融化烧断问题,采用外部过滤取样器解决高尘导致的堵塞问题,采用烟气温度控制方法解决卤化碱凝结问题。 相似文献
16.
17.
The present study aims at investigating MOCVD technique for the deposition of magnetic oxide thin films using volatile metal-organic
compounds as source material. A three-step scheme has been described to form γ-Fe2O3 phase starting from α-Fe2O3 films as-deposited in optically heated atmospheric cold wall CVD reactor. Growth of γ-Fe2O3 in a two-step process has been performed by depositing Fe3O4 phase directly by resistively heated low-pressure CVD (LPCVD) technique. Role of substrate temperature in controlling the
oxidation leading to direct formation of metastable γ-Fe2O3 phase (single-step scheme) by atmospheric CVD technique has been described. A new mode of introduction of cobalt in the film,
namely heterogeneous dispersion of cobalt in the γ-Fe2O3 matrix, has also been described. Crystallographic structure, microstructure and magnetic properties of the films have been
studied in detail. Biaxial vector coil and high-temperature magnetic studies were carried out for determining the nature of
anisotropy in the γ-Fe2O3 film. Growth of γ-Fe2O3 films in different schemes have been discussed from the studies of growth kinetics in a cold-and hot-wall-type reactor chambers. 相似文献
18.
La1−xNaxMn1−yNayO3 (0.12<x<0.16; 0.04<y<0.07) have been synthesized from NaBr and NaI fluxes at relatively low temperature of 850 and 750 °C, respectively. Final composition of these oxides was obtained from chemical analysis of the elements present. The flux grown oxides crystallize in the rhombohedral structure (space group R-3c, No. 167) and are ferromagnetic metals (FMM). Chemical analysis and Rietveld refinement of X-ray data indicate Na ion is substituted for both La- and Mn-sites in the compound prepared from NaBr and NaI fluxes with 33 and 49% of Mn4+ concentration, respectively. 相似文献