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1.
A model is proposed and checked experimentally to describe a direct relationship between the anisotropy of thin ferromagnetic
films and the texture of a low-symmetry magnetically ordered phase of CoFe alloy which has a monoclinic unit cell. The measured
distortions of the initial cubic cell are an order of magnitude greater than the magnetostriction constants of the solid sample.
An analysis is made of a system for the formation of anisotropic stresses in the plane of the film in which this effect is
attributed to the magnetic texture. A suitable method is developed for making diffraction measurements and analyzing the experimental
data.
Pis’ma Zh. Tekh. Fiz. 24, 51–56 (October 12, 1998) 相似文献
2.
The present status of the theory of saturation magnetization of ferromagnetic thin films is reviewed. The extensions of the Heisenberg trace method and the spin-wave method to the case of ferromagnetic thin films is fully discussed together with a comparison of the theoretical results with experimental data. The effect of anisotropic magnetic fields on magnetization and Curie temperature is presented, and the dependence of the magnetization and Curie temperature on film thickness is studied. Very recent progress and new results of the theory are stressed. The application of the Green function method to ferromagnetic thin films is also examined. 相似文献
3.
4.
Various applications of the Faraday and Kerr effects for the investigation of domain structures and reversal mechanisms in thin ferromagnetic films are reviewed. Different optical arrangements for the observation of domains are described and compared. Using magnetooptic microscopy domains and wall structures can be observed with a resolution of 1 μm. Magnetization structures give rise to diffraction phenomena, which are revealed as Fresnel fringes, Fraunhofer patterns, and dark field pictures. Applications of these phenomena and the consequences for the resolution of magneto-optic microscopy are discussed. Various kinds of reversal processes by wall motion or rotation, respectively, can be distinguished from each other by measuring the light intensity in two settings of the analyzer and by a dark field method. These reversal mechanisms can be identified even in case of fast switching when direct observations are not possible. Since the applications of magnetooptics are not restricted by any temperature limit, they are especially suited for the investigation of temperature dependent phenomena, e.g., the Barkhausen effect and the magnetic aftereffect. A picture of a domain structure in a gadolinium film at 80°K is shown. 相似文献
5.
Static wall coercive force in ferromagnetic thin films 总被引:1,自引:0,他引:1
The static wall coercive force of thin ferromagnetic films has been calculated from a model of conservative wall energy. The spatial dependence of the wall energy γw is assumed to be given by the mean value of the local anisotropy energy, averaged over a coupling volume of the wall. The result of the calculation shows thatH_{w} propto frac{S}{M_{s}} (frac{D}{W})^{1/2} frac{1}{L} where the structure constantS includes the local anisotropy,D is the mean diameter of a region with constant anisotropy (for instance crystallites),W is the wall width; andL is the coupling length parallel to the wall. 相似文献
6.
D. E. Oates P. P. Nguyen G. Dresselhaus M. S. Dresselhaus C. W. Lam S. M. Ali 《Journal of Superconductivity》1992,5(4):361-369
We present measurements of surface impedanceZ
S
as a function of frequency, temperature, and rf magnetic field for high-quality epitaxial YBa2Cu3O7–x
thin films using a striplineresonator technique that measures theQ of the resonator vs. input power. The results have been modeled using Ginzburg-Landau theory at moderate fields, and the Bean critical state model at high fields. Good agreement has been obtained between the model and the measurements. We also discuss the current distributions in the stripline for both low power whenZ
S
is linear and high power whenZ
S
is nonlinear. 相似文献
7.
Residual absorption in optical coatings and materials is directly measured by means of the laser-induced deflection (LID) technique. For transmissive coatings a measurement strategy is introduced that allows for the separation of different absorptions of the investigated sample (bulk, coating, surface) by use of only one sample. Laser irradiation yields absorption values between 2 x 10(-3) and 2.9 x 10(-2) for antireflecting and highly reflecting (HR) coatings at 193 nm and 30.6 x 10(-6) for a HR mirror at 527 nm. Use of laser-induced fluorescence at 193 nm excitation reveals trivalent cerium and prasodymium and hydrocarbons in different single layers and coatings. In addition to correlation with absorption data, the influence of a high fluorescence quantum yield on the absorption measurement is discussed. 相似文献
8.
9.
Co-doped SnO2 thin films are grown on sapphire (0001) substrates at 600 °C by the technique of dual-beam pulsed laser deposition. The prepared films show preferred orientation in the [100] direction of the rutile structure of SnO2. Nonequilibrium film growth process results in doping Co into SnO2 much above the thermal equilibrium limit. A Film with 3% of Co is ferromagnetic at room temperature with a remanent magnetization of ∼ 26% and a coercivity of ∼ 9.0 mT. As Co doping content x increases, the optical band gap absorption edge (E0) of the Co-doped SnO2 thin films initially shows a redshift at low x up to x = 0.12 and then increases at the higher x, which are attributed to the sp-d exchange interactions and alloying effects, respectively. 相似文献
10.
《Nanostructured Materials》1998,10(2):195-204
Surface segregation and phase separation in binary AB systems have been calculated in a slab consisting of atomic planes perpendicular to the free surfaces. For strongly segregating systems, if the average concentration lies in the two phase region of the binary phase diagram, a phase separation from the surfaces develops and two layers of the A-rich phase cover the A-poor central phase in the slab (lamellar structure). Furthermore, there is an enrichment (segregation) of A atoms in the near surface layers of the upper phase. For weakly segregating systems there exists a critical concentration Ch. If T > Th (Th is the temperature on the miscibility gap at Ch), a similar phase separation and segregation has been observed as above. However, for T < Th, two different phases can be in equilibrium in a columnar structure. The concentrations in their central layers, if the slab is thick enough, correspond to the compositions of the miscibility gap at the given temperature. At the same time, there is a strong segregation of A atoms in the A-poor phase, while, due to the stronger separation tendency, the minority B atoms will ‘separate’ at the surface, leading to a desegregation of A atoms in the A-rich phase. 相似文献
11.
The theory of phase transitions in magnetic systems with surfaces is reviewed. Results of the phenomenological Landau-Ginzburg theory as well the scaling theory are briefly presented and compared with those obtained for particular microscopic models. Possibilities of special kinds of magnetic phase transitions in systems with surfaces are also presented. 相似文献
12.
Using a general scattering matrix approach in the theoretical analysis the polar Kerr rotation is shown to have a marked dependence on sample thickness when the thickness is less than 60 nm. The polar Kerr rotation is calculated for thin films of iron and cobalt for normal incidence in the wavelength range 400–1400 nm for both unbloomed and bloomed specimens. 相似文献
13.
Horst Hoffmann 《Thin solid films》1979,58(2):223-233
The influence of film structure on magnetic properties is primarily due to the creation of spatially fluctuating local anisotropies which make the magnetization direction inhomogeneous. The deviation from homogeneous magnetization of domains, the so-called ripple, influences a great number of static, quasistatic and dynamic effects via the intrinsic demagnetizing field. The ripple theory is expressed in terms of only one phenomenological constant, the structure constant S, which covers completely the influence of the film structure on the deviations of real thin film behaviour from that of ideal single domains. 相似文献
14.
Collinear ferromagnetic spin ordering in a thin film with pinned surface spins is shown to be stable only for certain orientations of the magnetisation vector. Also, the magnon potential is shown to extend outward from the film surface; according to whether the surface spins are pinned more strongly or less strongly than the internal spins, the potential becomes infinite at a distance outward from the surface smaller or larger than one lattice constant. 相似文献
15.
The automatized scanning spectrometer of ferromagnetic resonance has been designed for measuring a distribution of in-plane magnetic anisotropy, effective saturation magnetization, coercivity, and other performances across the area of thin magnetic films (TMFs) in a monodomain state. The spectrometer is supplied with a set of plug-in measuring heads overlapping frequency band 0.1 /spl divide/ 6.0 GHz. The degree of locality of measurements in the range 0.3 /spl divide/ 2.5 mm is defined by the size of the measuring hole in the microstrip resonator built in the head. The signal-to-noise ratio of the heads is not less than 10 for permalloy film of 100-/spl Aring/ thickness when the locality of measurements is about 1 mm, and it can be increased considerably in the signal accumulation mode. Magnetic imaging is demonstrated with an example of purposely-stressed TMFs. 相似文献
16.
Viljami Pore Mukesh DimriHimani Khanduri Raivo SternJun Lu Lars HultmanKaupo Kukli Mikko RitalaMarkku Leskelä 《Thin solid films》2011,519(10):3318-3324
TiO2 thin films doped or mixed with cobalt oxide were grown by atomic layer deposition using titanium tetramethoxide and cobalt(III)acetylacetonate as metal precursors. The films could be deposited using both O3 and H2O as oxygen precursors. The films grown using water exhibited considerably smoother surface than those grown with ozone. The TiO2:Co films with Co/(Co + Ti) cation ratio ranging from 0.01 to 0.30 were crystallized by annealing at 650 °C, possessing mixed phase composition comprising rutile and anatase and, additionally, CoTiO3 or CoTi2O5. The annealed films demonstrated magnetic response expressed by magnetization curves with certain hysteresis and coercive fields. 相似文献
17.
M. Leon 《Journal of Materials Science》1990,25(1):669-672
Thin films of djurleite have been examined by TED in order to study the phase transition at 86° C. The samples were heated during observation in the electron microscope. Under these conditions no intermediate phase was found, but we have found two different orientations of the djurleite supercell with respect to the high chalcocite cell. The transformation matrix was determined. 相似文献
18.
The magnetic stiffness within ferromagnetic thin films, considered as a tendency of the film to be homogeneous with respect to the distribution of magnetization directions, is defined on the basis of the domain structure as well as of the spin wave theory. The transversal stiffness parameter in thin films is calculated by means of the band model approach within a Hartree-Fock type of approximation. This parameter depends on the film thickness and, what is particularly interesting, on the surface effects. 相似文献
19.
Ferromagnetic thin films have been sputtered from a modified conventional magnetron cathode (3" diameter). The targets (5 to 6 mm thick) were stainless steel, demagnetized SmCo5 and CoCr(15-18 at% Cr). The deposition rate was 6 nm/s at a power density of 15 W/cm2. Increasing the power rates up to 12 nm/s could be achieved. The saturation magnetization ranged from 0.4 to 1,5 Tesla. The films sputtered from stainless steel had a magnetization only 30 % smaller than the magnetization of Fe. The coercive force varied from 0.8 to 75 kA/m. 相似文献
20.
We investigate the mechanical response of 50-600?nm epitaxial Ge films on a Si substrate using nanoindentation with a nominally spherical (R≈4.3?μm) diamond tip. The inelastic deformation mechanism is found to depend critically on the film thickness. Sub-100?nm Ge films deform by pressure-induced phase transformation, whereas thicker films deform only by shear-induced dislocation slip and twinning. Nanoindentation fracture response is similarly dependent on film thickness. Elastic stress modelling shows that differing stress modes vary in their spatial distribution, and consequently the film thickness governs the stress state in the film, in conjunction with the radius of the nanoindenter tip. This opens the prospect of tailoring the contact response of Ge and related materials in thin film form by varying film thickness and indenter radius. 相似文献