Kerr effect enhancement in ferromagnetic films

The enhancement of the Kerr magneto-optic effect by overcoating a ferromagnetic film with a dielectric film is studied. It is treated as an impedance-matching problem for the light wave. Closed form solutions are obtained for the polar Kerr effect. The same analysis, with modifications, can be applied to the longitudinal Kerr effect. The effect of the dielectric thickness on the enhancement is continuously monitored with a laser beam (λ = 6328Å) during the dielectric film deposition. The amplification of the longitudinal Kerr signal with SiO films on iron film is of the order of five, and the enhancement varies periodically as a function of dielectric thickness. The experimentally observed period, 1600Å, agrees well with the calculated value. The sense ofB-Hloops, which also varies periodically as a function of the dielectric thickness, is explainable in terms of the phase factor which appears in the difference between the reflection coefficients.     

Thickness dependence of breakdown field in thin films

Studies of the thickness dependence of dielectric breakdown in thin films are of fundamental importance for the development of devices. Here a systematic study of the d.c. breakdown in “built-up” ionic films of barium stearate is reported in the thickness range (25–2000 Å). These films are ideally suited for such studies because of their perfect reproducibility and control of their thicknesses which are uniform and very accurately known. The breakdown strength is found to be a power dependent function of thickness as predicted by Forlani and Minnaja's theory based on an electron ionization avalanche mechanism. The films studied have recently been found to be promising for making devices.     

Refractive index of polycrystalline submicrometer polymer thin films: Thickness dependence

Dielectric films used in insulating applications are becoming consistently thinner, hence the thickness of thin and ultathin films is an important design parameter. There exists a need for characterizing and understanding the thickness dependence of properties of films. The refractive index for low dielectric polytetrafluoroethylene crystalline submicrometer thin films is investigated by using an optical spectrometer coupled with a hot stage to monitor their thickness-dependent behavior. It is demonstrated that the refractive index has a strong dependence on film thickness, which can be related to the microstructure and morphology of the film as characterized by Fourier transform infrared spectroscopy and scanning electron microscopy.     

Anisotropy of thin ferromagnetic films

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)     

Saturation magnetization in ferromagnetic thin films

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.     

Thickness dependence of electrical resistivity and activation energy in AgSbTe2 thin films

Thin films of AgSbTe₂ with different thicknesses were prepared by thermal evaporation on glass substrates held at room temperature. The films were all found to be semiconducting in nature. The film resistivity was found to be a function of inverse thickness and was discussed on the basis of the effective mean free path model. The activation energy was found to be a linear function of the inverse square of film thickness. It was attributed to the quantization of the momentum component of charge carriers normal to the film plane.     

Optimization of the planar hall effect in ferromagnetic thin films for device design

The planar Hall effect, although directly related to the magnetoresistance effect, differs in its potential uses by the disposition of the sensing electrodes allowing an internal balance of the excitation voltage drop. An experimental study of ferromagnetic thin film conditions of evaporation, film thickness, composition and shape of the electrodes has been undertaken. Anisotropic Ni-Fe films with various additions of Pd, V, Co, Mo, showed a maximum planar Hall effect for the composition 86-percent Ni, 14-percent Fe. The optimization of the geometrical parameters of the electrodes and the magnetic film elements is described, allowing one to design for maximum output voltage or maximum output current in a short circuited loop. Two schemes are presented for implementation of small NDRO memories.     

Thickness dependence of magnetic properties of Co90Fe10 nanoscale thin films

Ferromagnetic monolayers Co90Fe10 thin films with individual layer thicknesses 2, 6, and 8 nm were grown on thermally oxidized Si substrate and magnetic properties of these were investigated with Ferromagnetic resonance (FMR) technique at room temperature. The magnetoresistance (MR) of the samples were measured as a function of applied DC magnetic field and the thickness dependence of the MR was plotted. The FMR spectra were recorded for both parallel and perpendicular geometry. The X-band (9.5 GHz) FMR spectra and resonance field of samples were analyzed and fitted theoretically by using the Landau-Lifshits dynamic equation of motion for magnetization with the Bloch-Bloembergen type damping term. The computer programs have been written to extract the effective magnetization (M), g-values and spin-spin relaxation time (T2) fitting parameters. The thickness dependence of magnetic parameters has been obtained from experimental data by mean of a theoretical model.     

Magnetooptical investigations on thin ferromagnetic films

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.     

Thickness dependence of optical parameters for Ge–Se–Te thin films

The present work deals with thickness dependent study of the thin films of Ge₁₀Se_90 − xTe_x (x = 0, 10) chalcogenide glasses. Bulk samples of Ge₁₀Se₉₀ and Ge₁₀Se₈₀Te₁₀ have been prepared by melt quenching technique. Thin films (thickness d = 800 nm and 1100 nm) of the prepared samples have been deposited on glass substrate using vacuum evaporation technique. The optical parameters i.e. optical band gap (E_g^opt), absorption coefficient (α), refractive index (n) and extinction coefficient (k) are calculated from the transmission spectrum in the range 400–1500 nm. The optical band gap decreases with the increase of thickness from 1.87 ± 0.01 eV (d = 800 nm) to 1.80 ± 0.01 eV (d = 1100 nm) for Ge₁₀Se₉₀ and from 1.62 ± 0.01 eV (d = 800 nm) to 1.48 ± 0.01 eV (d = 1100 nm) for Ge₁₀Se₈₀Te₁₀ thin films.     

Thickness effect on the crystallization characteristic of RF sputtered Sb thin films

Journal of Materials Science: Materials in Electronics - The monobasic Sb thin films with different thicknesses were prepared by radio frequency magnetron sputtering. The evolutions of Sb thin film...     

Thickness dependence of microstructures and magnetic properties for CoPt/Ag nanocomposite thin films

Ag underlayer (30 nm) has improved the degree of ordering and perpendicular magnetic anisotropy of CoPt films (7.5-10 nm). After annealing at 600 °C and 700 °C, the perpendicular coercivity of CoPt/Ag films has been raised as the thicknesses of CoPt layers are increased. The magnetic easy axis of CoPt/Ag films would change from a random orientation to an out-of-plane orientation. It is found that Ag underlayer with thickness of 30 nm can improve the perpendicular magnetic properties of CoPt layers with thicknesses in the range of 7.5-10 nm. The CoPt/Ag films would be a candidate for perpendicular magnetic recording media.     

Static wall coercive force in ferromagnetic thin films

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 γwis 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 constantSincludes the local anisotropy,Dis the mean diameter of a region with constant anisotropy (for instance crystallites),Wis the wall width; andLis the coupling length parallel to the wall.     

厚度对DLC薄膜内应力的影响研究

采用ECR微波等离子体增强化学气相沉积的方法于C1H2/H2/Ar2等离子环境中在单晶Si(111)晶面上制备了不同厚度的DLC膜样品,研究了薄膜的厚度随沉积时间的变化及薄膜的硬度、内应力随厚度的变化关系.结果表明,在沉积时间变化范围内,厚度与沉积时间基本呈线性关系,沉积速率可达80nm/min;制备态样品存在的内应力...     

Thickness dependence of electrical properties in thin films of undoped indium oxide prepared by ion-beam sputtering

Preparation and electrical characterization of undoped indium oxide films were examined as a function of thickness and annealing. Thin films ranging from 1.1 to 113 nm thickness were deposited on glass substrates by ion-beam sputtering. Low-angle X-ray diffraction analysis in multi-layered films showed the possibility that physically continuous and almost flat films were formed even in the thinnest 1.1 nm films. Room temperature resistivity of as-deposited films decreased sharply by more than five orders of magnitude as the thickness increased from 1.1 to 5.2 nm. The 2.4 nm thick films, in its as-deposited state, showed a gradual resistivity modulation with the change of atmosphere between air and argon gas at room temperature. Annealing at 300° C for 5 h in air increased the resistivity drastically; the room temperature resistivity of 24.3 nm thick films changed from 2.2×10^–3 cm (as-deposited) to higher than 10⁵ cm (annealed).