Domain Structure Of Thin Films Research Articles

The effect of thickness and annealing treatment on microstructure and magnetic properties of amorphous Fe-Si-B-P-C thin films

To develop an excellent low-dimensional magnetic material, the evolution of microstructure and soft magnetic properties in thin films with thickness as well as annealing treatment has been systematically investigated. Fe-Si-B-P-C thin films were fabricated using radio frequency magnetron sputtering. Microstructure of as-deposited and as-annealed thin films with various thicknesses have been characterized, and corresponding soft magnetic properties have been studied. The magnetic domain structure in thin films was further characterized via the magneto-optical Kerr microscope. It is revealed that all these as-deposited thin films exhibit a columnar structure, and the surface roughening is in accordance with the anomalous scaling. The coercivity gradually decreases from 4.8 Oe for 61 nm-thick film to 0.6 Oe for 608 nm-thick film, and almost remains constant with further increasing thickness, while the magnetic impedance ratio rises with thickness. After 473 K-annealing treatment coercivity decreases and magnetic impedance ratio increases, which can be attributed to the release of residual stress and the enhanced exchange coupling. After annealing at 573 K, although no obvious improvement in coercivity occurs, magnetic impedance ratio further rises due to the enhanced electrical conductivity and the reduced magnetic anisotropy. Severe crystallization takes place after annealed at 673 K, deteriorating soft magnetic properties of thin films. Therefore, the 573 K-annealed Fe-Si-B-P-C thin film with 1210 nm in thickness exhibits the best soft magnetic properties, having coercivity of 0.3 Oe, magnetic impedance ratio of 66.2% and relatively low magnetic anisotropy, which is a very promising soft magnetic material for sensor application.

Finite element micromagnetic simulation of the magnetic domain structures in thin films with uniaxial anisotropy

In this work, finite element micromagnetic simulations were performed in order to study the magnetization reversal mechanisms in thin films with perpendicular magnetocrystalline anisotropy. Magnetization loops are taken both for perpendicular and planar external magnetic fields, at different anisotropy constants and film sizes. Magnetization vortices, stripe domains and magnetic bubbles are ab initio simulated and they are investigated on the basis of the film characteristics.

Resonant soft x‐ray scattering and reflectivity study of the phase‐separated structure of thin poly(styrene‐b‐methyl methacrylate) films

AbstractCombined soft X‐ray scattering and reflectometry techniques promise analysis of polymer thin film domain structure and composition without resorting to chemical modification or isotopic labeling. This work explores the capabilities of these techniques in polymer films of poly(styrene‐b‐methyl methacrylate) (P(S‐b‐MMA)). The results demonstrate that the techniques give detailed information on the domain structure of thin films using well‐known modeling procedures. Discrepancies were noted between the X‐ray optical parameters that are needed to best fit the reflectivity data to the model and the expected parameters. The sources of these discrepancies are discussed in terms of instrument configuration parameters, sample attributes, and, particularly, anisotropy of the chromophore parameters. The results show that fitting the soft X‐ray reflectivity data is much more sensitive to these X‐ray optical parameters than the soft X‐ray scattering data. Nevertheless, fits to both types of data yield quantitative measures of the polymer film's lamellar morphology that are consistent with each other and with literature values. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013

Formation of phase domain structures in thin films under conditions of a first-order magnetic phase transition

This paper reports on the results of a theoretical investigation into the magnetic and resonance properties of thin films in the range of the transition from a paramagnetic state to a ferromagnetic state in the case where the magnetic transition is a first-order phase transformation. It is demonstrated that, in an external magnetic field directed perpendicular to the film plane, the formation of a specific domain structure consisting of domains of the coexisting paramagnetic and ferromagnetic phases can appear to be energetically favorable. The parameters of the equilibrium system of stripe phase domains and their dependences on the temperature, the magnetic field, and the characteristics of the material are calculated. The specific features of the magnetic resonance spectra under the conditions of formed stripe phase domains are considered. A relationship is derived for the dependence of the resonance field of the system of ferromagnetic domains on the magnetization and temperature. It is shown that the alternating external field can fulfill an orientation function in the formation of stripe phase domains.

Phase‐Field Method of Phase Transitions/Domain Structures in Ferroelectric Thin Films: A Review

This article briefly reviews recent applications of phase‐field method to ferroelectric phase transitions and domain structures in thin films. It starts with a brief introduction to the thermodynamics of coupled electromechanical systems and the Landau description of ferroelectric transitions in homogeneous ferroelectric single crystals. The thermodynamic potentials of a homogeneous crystal under different mechanical boundary conditions are presented, including the thin‐film boundary conditions. The phase‐field approach to inhomogeneous systems containing domain structures is then outlined. It describes a domain structure using the spatial distribution of spontaneous polarization. The evolution of a domain structure towards equilibrium is driven by the reduction in the total‐free energy of an inhomogeneous domain structure including the chemical driving force, domain wall energy, electrostatic energy as well as elastic energy. A number of examples are discussed, including phase transitions and domain stability in ferroelectric thin films and superlattices. It is demonstrated that using a set of independently measured thermodynamic parameters for the corresponding bulk single crystals, the phase‐field approach is able to quantitatively predict not only the strain effect on phase transition temperatures but also the correct ferroelectric domain structures for a given strain and temperature.

Studies of Magnetic Microstructures With Soft X-Ray Transmission Microscopy

We review recent achievements of magnetic full-field soft X-ray transmission microscopy. This technique allows for an element-specific imaging of magnetic domain structures in thin films and nanopatterned elements. With a lateral resolution down to 15 nm, the ability to record images in external magnetic fields and the application of stroboscopic pump-and-probe schemes detailed insights into fundamental mechanisms of micromagnetism can be obtained which are relevant in the development of high density and ultrafast magnetic storage and sensor technologies.

Magnetic domain structure in thin film under alternate magnetic field

Abstract Magnetic domain structures in a garnet thin film under alternate magnetic fields have been investigated. In alternate magnetic fields, a labyrinth structure approaches a parallel-stripe structure. The competition among the segment clusters, in which stripes have different directions, causes stable dynamical domain structures. With the increase of the amplitude of alternate fields, the segment clusters become small.

Effect of electrical boundary conditions on ferroelectric domain structures in thin films

The domain structures in a ferroelectric thin film are studied using a phase-field model. A cubic-to-tetragonal ferroelectric phase transition in lead titanate thin film is considered. Both elastic interactions and electrostatic interactions are taken into account. The focus is on the effect of electrical boundary conditions on the domain morphologies and volume fractions. It is shown that different electric boundary conditions may have a significant effect on the domain structures.

Effect of substrate constraint on the stability and evolution of ferroelectric domain structures in thin films

The stability and evolution of ferroelectric domain structures in thin films are studied. Elastic solutions are derived for both elastically anisotropic and isotropic thin films with arbitrary domain structures, subject to the mixed stress-free and constraint boundary conditions. These solutions are employed in a three-dimensional phase-field model to investigate simultaneously the effect of substrate constraint and temperature on the volume fractions of domain variants, domain-wall orientations, surface topology, domain shapes, and their temporal evolution for a cubic-to-tetragonal ferroelectric phase transition. A specific example of a [001] orientated film heteroepitaxially grown on a [001] cubic substrate is considered. It is shown that the shapes of a-domains with tetragonal axes parallel to the film surface are significantly different from those of c-domains with tetragonal axes perpendicular to the film surface. For the substrate constraints and temperatures under which both a- and c-domains coexist, both types of a-domains are present with their tetragonal axes perpendicular to each other, and the domain wall orientations deviate from the 45 orientation generally assumed in thermodynamic analyses. It is demonstrated that a substrate constraint results in sequential nucleation and growth of different tetragonal domains during a ferroelectric phase transition.

Three-Dimensional Information on the Phase Domain Structure of Thin Films of Polymer Blends Revealed by Secondary Ion Mass Spectrometry

We describe the technique of dynamic secondary ion mass spectrometry developed to determine three-dimensional phase domain structures of films of polymer blends. The polymers are composed of light elements or are labeled with deuterium or heavy elements. The applicability of this method to various polymer blends forming thin and ultrathin films with flat and undulated air/film interface is discussed.

Scanning force microscopy: Application to nanoscale studies of ferroelectric domains

Recent advances in nanoscale studies of ferroelectric domains by means of scanning force microscopy (SFM) are reviewed with particular emphasis on investigation of domain structure and polarization reversal in ferroelectric thin films. Applicability of different SFM modes to domain imaging with respect to the physical properties of ferroelectrics is discussed. Examples shown here include results on domain structure observation in single crystals and films by SFM operating in the noncontact, friction, topographic and piezoresponse modes. Domain wall dynamics and fatigue effects as well as SFM spatial resolution of domain structure in thin films are addressed.

Structure Formation via Polymer Demixing in Spin-Cast Films

The domain structure in thin films of an immiscible polystyrene/poly(methyl methacrylate) (PS/PMMA) blend was studied after spin-casting from a common solvent. Atomic force microscopy (AFM) combined with selective dissolution was used to obtain three-dimensional information on the domain morphology in thin films. Three different common solvents and three different substrate surfaces were studied. Distinct differences in the thin film domain structure and surface topography are observed depending on the substrate surface energy and the solubility of the two polymers in the three solvents. The topographic modulation can be explained by a different rate of solvent evaporation during spin-coating for the two phases. The normal and lateral organization of the phase-separated domains is governed by a complex interplay between preferential aggregation of one phase at the substrate and phase segregation in the film. Additionally, some of the results suggest that a dewetting process may be involved in the domain f...

Domain wall jaggedness induced by the random anisotropy orientation in magneto-optic materials: A computer simulation study

Computer simulations of magnetic domain structure in thin films of amorphous rare-earth transition metal magneto-optic recording media are performed. In these simulations, the recording media are two-dimensional lattice of 64×64 magnetic moments with a lattice distance of 10 Å. The motion of the magnetic moments follows the dynamic Landau–Lifshitz–Gilbert (LLG) equation under the influence of an effective field arising from the local anisotropy, nearnest-neighbor exchange, classical dipole–dipole interaction, and an external applied field. Within the constraints of the LLG equation, we have investigated the process of domain wall formation for a medium with random anisotropy orientation. Even for very small randomness of anisotropy orientation, it is found that the 2π-Bloch wall line appears at the boundaries of magnetic domains and the domain wall is jagged. Finally, the effects of exchange stiffness coefficient Ax and anisotropy coefficient Ku on the wall width and the jaggedness which measured the straightness of domain wall are studied.

Coherent Foucault imaging: A method for imaging magnetic domain structures in thin films

A method for imaging magnetic domain structures in the transmission electron microscope is described. Coherent Foucault imaging provides a direct means of producing a magnetic interferogram which reveals the quantitative distribution of magnetic induction across the specimen. The technique requires the high coherence of a field-emission gun system and the ability to position an aperture accurately to cut part of the diffraction pattern. A simple analytical theory, together with computer simulations and experimental results, is presented to demonstrate the power of the technique.

A simplified mode of differential phase contrast Lorentz microscopy.

A simplified mode of differential phase contrast Lorentz microscopy for the study of magnetic domain structures in thin films is proposed and demonstrated. This mode employs a single annular detector in a scanning transmission electron microscope rather than the specialized split detectors that have been previously used. The resulting signal is sufficiently linear with magnetic field strength to allow quantitative data to be obtained on the domain configurations and the natures of the domain walls.

Domain structure of thin films of Fe-Cr-Co alloy

Domain structure of thin films of Fe-Cr-Co alloy

Transitional periodic domain structure in thin films of magnetically uniaxial materials

The paper gives the theory of transitional domain structure in thin films of uniaxial ferromagnets with easy axis perpendicular to the film. It is proved that in a certain range of thicknesses this structure is energetically more advantageous than the plate structure originally proposed by Kittel. The proposed model explains the transition from the Kittel structure to the homogeneously magnetized film.

Magnetic domain structure in thin crystals of cobalt

Abstract Quantitative electron microscope observations of a strip domain structure in thin films of cobalt produced by electropolishing from bulk annealed specimens are given and interpreted in terms of an energy minimization model based on calculations of Malek and Kambersky (1958). The observations are consistent with the model within the experimental uncertainties. However, there appears to be a systematic trend in the data which suggests that more accurate experiments may lead to disagreement.

On the theory of the domain structure of thin films of magnetically uni-axial materials

The demagnetizing energy is calculated of a, simple model of the domain structure of a magnetically uni-axial thin film, the axis of easy magnetization of which is perpendicular to the surface. The width of the domain, and for the case of MnBialso the total energy of the domain structure, are found as functions of the thickness of the film.

Magnetic Writing on Thin Films of MnBi

A study has been made of the domain structure of thin films (∼1000 A) of MnBi and their capability of storing information magnetically. It is estimated that a million bits of information could be written on a square centimeter of film. The information can be read out optically by utilizing the Faraday effect. The films have a uniaxial direction of easy magnetization normal to their surfaces and retain their magnetization after saturation along this direction in spite of the large demagnetizing factor. When magnetized in this manner, a high optical contrast is obtained between the writing and the background.