Investigation Of Domain Structure Research Articles

Collective control of a vortex array in a ferroelectric ultrathin film

Recently, the observation of ferroelectric vortex arrays has triggered the investigation of topological domain structures and their characteristics. Vortices are typical topological domain structures with chirality in nanoscale ferroelectric materials. The chirality of a single vortex in a nanodot can be easily manipulated, but the collective control of a vortex array is exceptionally difficult and has not yet been realized. This Letter proposes an effective scheme for the collective control of a vortex array and investigates it via phase-field simulations. The results indicate that the collective control of a vortex array with bidirectional switching can be realized by introducing a bending film with periodic large curvatures under alternative electric fields. Furthermore, a general rule for determining the electrically controllable chirality of ferroelectric vortices is proposed. This Letter demonstrates the feasibility of the collective control of vortex arrays and provides insights for developing ferroelectric nanoelectronic devices based on vortex arrays.

Investigation of magnetization reversal and domain structures in perpendicular synthetic antiferromagnets by first-order reversal curves and magneto-optical Kerr effect

Perpendicular synthetic-antiferromagnet (p-SAF) has broad applications in spin-transfer-torque magnetic random access memory and magnetic sensors. In this study, the p-SAF films consisting of (Co/Ni)3]/Ir(t Ir)/[(Ni/Co)3 are fabricated by magnetron sputtering technology. We study the domain structure and switching field distribution in p-SAF by changing the thickness of the infrared space layer. The strongest exchange coupling field (H ex) is observed when the thickness of Ir layer (t Ir) is 0.7 nm and becoming weak according to the Ruderman–Kittel–Kasuya–Yosida-type coupling at 1.05 nm, 2.1 nm, 4.55 nm, and 4.9 nm in sequence. Furthermore, the domain switching process between the upper Co/Ni stack and the bottom Co/Ni stack is different because of the antiferromagnet coupling. Compared with ferromagnet coupling films, the antiferromagnet samples possess three irreversible reversal regions in the first-order reversal curve distribution. With t Ir increasing, these irreversible reversal regions become denser and smaller. The results from this study will help us understand the details of the magnetization reversal process in the p-SAF.

Investigation of Electronic States and Magnetic Domain Structure of La1 – xSmxMn2Si2 (x = 0, 0.25) Layered Intermetallic Compounds by Resonant Photoemission Spectroscopy and Magnetic Force Microscopy

Investigation of Electronic States and Magnetic Domain Structure of La1 – xSmxMn2Si2 (x = 0, 0.25) Layered Intermetallic Compounds by Resonant Photoemission Spectroscopy and Magnetic Force Microscopy

Investigation of domain structures in monomethoxy poly(ethylene glycol)‐b‐poly(caprolactone) grafted poly(acrylic acid) by NMR diffusion studies

AbstractAssociating polymers developed by grafting a block copolymer of monomethoxy poly(ethylene glycol)‐b‐poly(caprolactone) (MPEG‐b‐PCL) onto poly(acrylic acid) undergo an irreversible sol–gel transition on heating. The influence of various physicochemical parameters on the thermoresponsive behaviour was examined by rheology and NMR studies. Pulsed field gradient NMR diffusion studies were performed to probe the mechanism of thermally induced gelation. Analysis of the diffusion data reveals the presence of loosely and strongly associated structures which respond differently to variation in temperature. It is observed that the polymer solution, which is visibly homogeneous, is heterogeneous on a mesoscopic scale with a distribution of domains. Detailed investigation of the thermally induced sol–gel transition shows that the mechanism of gelation involves irreversible alterations in the domain structure and size. © 2022 Society of Industrial Chemistry.

Digital holographic microscopy for domain structure investigation of triglycine sulfate monocrystals doped with Nd

The domain structure is an important characteristic of ferroelectrics. One of the most intensively studied ferroelectrics is triglycine sulfate (TGS). Although many methods have been developed for the observation of the domain structure in TGS, it still cannot be visualized routinely. A new method for observation of the domains in TGS, in particular digital in-line holographic microscopy, was applied for investigation of the domain structure of TGS monocrystals doped with Nd. Monocrystals of TGS with different concentration of Nd in the solution of growth were investigated. The size of the domains was calculated using appropriate software. The results show that the average size of domains increases with the increase of the Nd concentration in the doped TGS monocrystals. Correlation analysis was applied to study the effect of Nd concentration on the domains area. A very strong, positive effect of Nd concentration on the area was established (R = 0.958 *). The established influence of the dopant concentration on the domains area is presented in analytical form through a mathematical model.

Investigation of domain structure in ferroelectric thin films by means of the Ising model

The domain structure in thin ferroelectric films was investigated in the framework of the modified Ising model with short-range exchange and long-range dipole-dipole interactions. The depolarizing field was also taken into account for the study of size effects in thin films. This field is the dominant factor influencing on the existence of phase transitions in the films. We used Monte Carlo method with the standard Metropolis algorithm to generate configurations on three-dimensional cubic lattices. The domains sizes were calculated in the longitudinal and transverse directions relatively to the spontaneous polarization direction. Temperature dependences of the domain sizes are obtained for different values of interaction constants. It was proved that the introduction of the depolarizing field leads to the appearance of a dead layer on the film boundaries. The dead layer thickness increases with increasing temperature. At a certain temperature (not equal to the Curie temperature), the dead layer is destroyed. The temperature dependences of the dielectric susceptibility at different film thicknesses have been calculated. It was shown that these dependencies have two maxima. The first maximum corresponds to a phase transition, the second one exists only for only thin films and corresponds to the destruction of the dead layer.

Investigation of the Domain Structure of Co-based Microwires by Magneto-Optical Indicator Films Method

The investigation of domain structure of Co-based microwires with negative magnetostriction was provided by magnetooptical method of indicator films. The thickness of the domain layer and the width of the surface domains were determined. It has been suggested that in thin microwires (with the diameter of about several tens of microns) with negative magnetostriction, the Neel-type of domain walls between the domains of the surface layer are observed. A number of assumptions about the regularities of the surface domain structure formation of microwires with negative magnetostriction have been put forward.

Colloid-SEM method for the investigation of magnetic domain structures

The paper presents scanning electron microscopy (SEM) studies on the magnetic domain structure (DS) using magnetic colloid. The possibility of colloid-SEM method for observing the DS of mono- and polycrystalline samples in the secondary (SEI) and backscattered electrons modes (BEC) is demonstrated. Owing to the large focal depth of SEM, it is possible to observe the overall DS and fine features, even in unpollished samples.

Hierarchical domain structures in (Pb,La)(Zr, Sn, Ti)O3 antiferroelectric ceramics

(Pb, La)(Zr, Sn, Ti)O3 (PLZST) ceramic is one of the most prospective antiferroelectric (AFE) materials for variety of functional applications including energy storage and converter. Systematic structural investigation of domain structures should be of fundamental importance for understanding the structure-property relationship in AFE ceramics. In this study, the hierarchical domain structures and modulated structures correlated to the compositional variation in (Pb0.97La0.02) (Zr0.50SnxTi0.50-x)O3 (x = 0.375, 0.45 and 0.50) were observed and investigated in details by transmission electron microscopy. The PLZST ceramics show exclusively incommensurate modulated structures (IMS) whose modulation period changed from 9.37 to 6.15 and to 4.04 with increasing of the x value. The hierarchical domain structures include, in decreasing scales, AFE domains, incommensurate domains and nanodomains. The elementary domains in PLZST ceramics are pinstriped nanodomains which were formed based on IMS configuration but by frequent modulation of IMS periodicity and formation of faults. Nanodomains accumulated and then dissociated into incommensurate domains and AFE domains successively. The presently revealed structural characteristics in antiferroelectric PLZST may stimulate future researches on the evolution of IMS-based hierarchical domains under external physical fields, e.g. thermal or electrical, and their correlation to the physical performance.

Round robin comparison on quantitative nanometer scale magnetic field measurements by magnetic force microscopy

Magnetic force microscopy (MFM) can be considered as a standard tool for nano-scale investigation of magnetic domain structures by probing the local stray magnetic field landscape of the measured sample. However, this generally provides only qualitative data. To quantify the stray magnetic fields, the MFM system must be calibrated. To that end, a transfer function (TF) approach was proposed, that, unlike point probe models, fully considers the finite extent of the MFM tip. However, albeit being comprehensive, the TF approach is not yet well established, mainly due to the ambiguities concerning the input parameters and the measurement procedure. Additionally, the calibration process represents an ill-posed problem which requires a regularization that introduces further parameters. In this paper we propose a guideline for quantitative stray field measurements by standard MFM tools in ambient conditions. All steps of the measurement and calibration procedure are detailed, including reference sample and sample under test (SUT) measurements and the data analysis. The suitability of the reference sample used in the present work for calibrated measurements on a sub-micron scale is discussed. A specific regularization approach based on a Pseudo-Wiener Filter is applied and combined with criteria for the numerical determination of a unique regularization parameter. To demonstrate the robustness of such a defined approach, a round robin comparison of magnetic field measurements was conducted by four laboratories. The guideline, the reference sample and the results of the round robin are discussed.

Advanced aperture cantilevers made by focused ion beam for both magnetic domain structure and morphology investigation in high resolution magneto optical microscopy

Magneto-optical microscopy is a well-known and widely used method of magnetic domain structure investigation. Spatial resolution is limited by diffraction limit of the light and practically not exceed 0.5μm. Possibility to overcome diffraction limit by combination of magneto-optical microscopy and magnetic-force microscopy was showed earlier [1]. Aperture cantilever was used to light up the sample in near-field mode. In this paper, authors review most popular technology for aperture cantilever production with its advantages and disadvantages. Authors propose new technology based on focused ion beam treatment for creation aperture cantilevers with advanced parameters such as small aperture size and light throughput. Bi-substituted yttrium iron garnet (Bi: YIG) thin films with high magneto-optical activity and different period of domain structure were used as test objects. High resolution images of both morphology and domain structure obtained with new advanced aperture cantilevers are shown.

Thickness Dependent Surface Topography, Magnetic Properties and Magnetic Domain Structure of Amorphous FeTaC Thin Films

We report systematic investigation of thickness dependent surface topography, magnetic properties and magnetic domain structures of amorphous Fe80Ta8C12 (x nm) films with x=5–100 nm. All the as-deposited films fabricated directly on thermally oxidized Si substrate at ambient temperature using magnetron sputtering technique exhibit amorphous structure. The structural studies reveal that island-like structure in ultra-thin films transforms into continuous one with increasing x>10. In addition, the average surface roughness increases with increasing x, but without any systematic dependency on x. Room temperature magnetic properties illustrate that the paramagnetic nature observed for films with x 97%), low coercivity (HC 3.5 kA/m) and HS (>40 kA/m) and reduced MR/MS (<45%). The magnetic domain studies not only reveal that the domains change from in-plane magnetization to dense stripe domain pattern with increasing x due to enhancement of effective magnetic anisotropy caused by stress quenched in during deposition, but also confirm that films with 12<x<40 exhibit in-plane magnetization with uniaxial anisotropy. High temperature thermomagnetization reveal a clear magnetic phase transition from ferromagnetic to paramagnetic state at relatively higher temperature of about 530 K. The observed results are elucidated on the basis of enhanced effective magnetic anisotropy, change in the magnetic domain structure and magnetic disorder with increasing FeTaC film thickness.

Magnetic Force Microscopy of Nanostructured Co/Pt Multilayer Films with Perpendicular Magnetization.

We present the results of magnetic force microscopy investigations of domain structures in multilayer [Co (0.5 nm)/Pt (1 nm)]5 thin film structures (denoted hereafter as Co/Pt) modified by additional Co capping layers and by ion irradiation. It is demonstrated that a Co capping layer essentially changes the domain structure and decreases the threshold of magnetization reversal, due to the formation of noncollinear magnetization in Co/Pt. It is shown that local irradiation with a focused He+ ion beam enables the formation of regions with decreased easy-axis anisotropy (magnetic bubbles) that have the inverse magnetization direction in the demagnetized state of Co/Pt. The experimental results demonstrate that the magnetic bubbles can be switched using a probe of a magnetic force microscope. The possible application of these effects for the development of magnetic logic and data storage systems is discussed.

Magnetic domain structure investigation of Bi: YIG-thin films by combination of AFM and cantilever-based aperture SNOM

We present the results of magnetic domain structure investigation by combination of atomic force microscopy (AFM) and scanning near-field optical microscopy (SNOM). Special hollow-pyramid AFM cantilevers with aperture was used. This combination allows us use same probe for both topography and domain structure visualization of Bi -substituted ferrite garnet films of micro- and nano-meter thickness. Samples were excited through aperture by tightly focused linearly polarized laser beam. Magneto-optical effect rotates polarization of transmitted light depend on domain orientation. Visualization of magnetic domains was performed by detecting cross polarized component of transmitted light. SNOM allows to obtain high resolution magnetic domain image and prevent sample from any disturbance by magnetic probe. Same area SNOM and MFM images are presented.

Effective magnetic anisotropy manipulation by oblique deposition in magnetostatically coupled Co nanostrip arrays

We report on an experimental investigation of magnetic properties and domain structure of single nanostrips and their magnetostatically coupled arrays possessing the shape anisotropy and anisotropy induced by oblique deposition, which are oriented at different angles to each other. The orientation of the effective anisotropy and the value of coercive force of nanostrip arrays depends on the angle between directions of the induced anisotropies. Micromagnetic simulations, performed to determine possible spin configurations especially within domain walls, support the experimentally observed magnetic domain structure. An influence of dipole-dipole interaction between magnetostatically coupled nanostrips on the domain structure and coercive force of arrays are discussed. We demonstrate the experimental validation of an early-proposed theoretical model for determination of the effective magnetic anisotropy through the combination of induced anisotropies.

On detector linearity and precision of beam shift detection for quantitative differential phase contrast applications

Differential phase contrast is a STEM imaging mode where minute sideways deflections of the electron probe are monitored, usually by using a position sensitive device (Chapman, 1984 [1]; Lohr et al., 2012 [2]) or, alternatively in some cases, a fast camera (Müller et al., 2012 [3,4]; Yang et al., 2015 [5]; Pennycook et al., 2015 [6]) as a pixelated detector. While traditionally differential phase contrast electron microscopy was mainly focused on investigations of micro-magnetic domain structures and their specific features, such as domain wall widths, etc. (Chapman, 1984 [1]; Chapman et al., 1978, 1981, 1985 [7–9]; Sannomiya et al., 2004 [10]), its usage has recently been extended to mesoscopic (Lohr et al., 2012, 2016 [2,12]; Bauer et al., 2014 [11]; Shibata et al., 2015 [13]) and nano-scale electric fields (Shibata et al., 2012 [14]; Mueller et al., 2014 [15]). In this paper, the various interactions which can cause a beam deflection are reviewed and expanded by two so far undiscussed mechanisms which may be important for biological applications. As differential phase contrast microscopy strongly depends on the ability to detect minute beam deflections we first treat the linearity problem for an annular four quadrant detector and then determine the factors which limit the minimum measurable deflection angle, such as S/N ratio, current density, dwell time and detector geometry. Knowing these factors enables the experimenter to optimize the set-up for optimum performance of the microscope and to get a clear figure for the achievable field resolution error margins.

Domain structure investigation of triglycine sulfate by digital in-line holographic microscopy

abstractThe domain structure is an important characteristic of ferroelectrics. One of the most intensively studied ferroelectrics is triglycine sulfate (TGS). The domains in TGS cannot be observed directly by usual optical methods. Many methods have been developed for the observation of the domain structure in TGS like: the etching method, the powder deposition method, the decoration method, the nematic liquid crystal method, the pyroelectric probe technique, the cleavage method, the scanning electron microscopy method, and others. Despite of all these efforts, the domain structure in TGS still cannot be visualized routinely. We suggest a new method for observation of the domains in TGS, in particular digital in-line holographic microscopy (DILHM). DILHM allows direct visualization of the domain structure, without any preliminary preparation of the samples. A big advantage of the new method is its ability to extract information about the change of the domain structure in depth from one digital hologram only.

Computational and experimental investigations of magnetic domain structures in patterned magnetic thin films

The use of nondestructive magnetic signatures for continuous monitoring of the degradation of structural materials in nuclear reactors is a promising yet challenging application for advanced functional materials behavior modeling and measurement. In this work, a numerical model, which is based on the Landau–Lifshitz–Gilbert equation of magnetization dynamics and the phase field approach, was developed to study the impact of defects such as nonmagnetic precipitates and/or voids, free surfaces and crystal orientation on magnetic domain structures and magnetic responses in magnetic materials, with the goal of exploring the correlation between microstructures and magnetic signatures. To validate the model, single crystal iron thin films (~240 nm thickness) were grown on MgO substrates and a focused ion beam was used to pattern micrometer-scale specimens with different geometries. Magnetic force microscopy (MFM) was used to measure magnetic domain structure and its field-dependence. Numerical simulations were constructed with the same geometry as the patterned specimens and under similar applied magnetic field conditions as tested by MFM. The results from simulations and experiments show that 1) magnetic domain structures strongly depend on the film geometry and the external applied field and 2) the predicted magnetic domain structures from the simulations agree quantitatively with those measured by MFM. The results demonstrate the capability of the developed model, used together with key experiments, for improving the understanding of the signal physics in magnetic sensing, thereby providing guidance to the development of advanced nondestructive magnetic techniques.

Visualization of Bulk Magnetic Properties by Neutron Grating Interferometry

The neutron Grating Interferometer (nGI) is a standard user instrument at the cold neutron imaging beamline ICON (Kaestner, 2011) at the neutron source SINQ at Paul Scherrer Institute (PSI), Switzerland. The setup is able to deliver simultaneously information about the attenuation, phase shift (DPC) (Pfeiffer, 2006) and scattering properties in the so-called dark-field image (DFI) (Grünzweig, 2008-I) of a sample. Since neutrons only interact with the nucleus they are often able to penetrate deeper into matter than X-rays, in particular heavier materials. A further advantage of neutrons compared to X-rays is the interaction of the neutron's magnetic moment with magnetic structures that allows for the bulk investigation of magnetic domain structures using the nGI technique (Grünzweig, 2008-II). The nGI-setup and its technique for imaging with cold neutrons is presented in this contribution. The main focus will be on magnetic investigations of electrical steel laminations using the nGI technique. Both, grain-oriented (GO) and non-oriented (NO) laminations will be presented. GO-laminations are widely used in industrial transformer applications, while NO-sheets are common in electrical machines. For grain-oriented sheet, domain walls were visualized individually,spatially resolved, while in NO-sheet a relative density distribution is depicted.

Domain structure investigation of non-stoichiometric strontium ferrites and cobaltites

Monte Carlo domain structure simulation and Debye equation calculation of XRD patterns were used to confirm the formation of domain structure and investigate its peculiarities. Correspondence of simulated XRD patterns with synchrotron powder diffraction experiments is achieved on the conditions that beside of 90o rotations of brownmillerite-like domains inside perovskite-like matrix each domain contains areas with perpendicularly oriented tetrahedral chains. Influence of such parameters as stoichiometry, average domain size, orthorhombic distortion degree on the XRD patterns is considered.