Static Domain Structures Research Articles

Domain structure evolution during polarization reversal in calcium orthovanadate single crystals

The domain structure evolution under the action of the series of rectangular electric field pulses at the elevated temperature has been studied by in situ optical imaging in calcium orthovanadate single crystal with an as-grown domain structure. In contrast to the usual continuous domain wall motion, the arising of domains with immovable walls at the surface as a result of ledge growth from the charged domain wall (CDW) was obtained. The imaging of the static domain structure at the polar surface allowed for determining the correlation between positions of the domains and CDWs. The switching after termination of the external field was observed.

Control of Dynamics in Weak PMA Magnets

We have recently shown that a hybrid magnetic thin film with orthogonal anisotropies presenting weak stripe domains can achieve a high degree of controllability of its ferromagnetic resonance. This work explores the origin of the reconfigurability through micromagnetic simulations. The static domain structures which control the thin film resonance can be found under a deterministic applied field protocol. In contrast to similar systems reported, our effect can be obtained under low magnetic fields. We have also found through simulations that the spin wave propagation in the hybrid is nonreciprocal: two adjacent regions emit antiparallel spin waves along the stripe domains. Both properties convert the hybrid in a candidate for future magnonic devices at the nanoscale.

The Insulator–Insulator and the Insulator–Mixed‐Metal–Insulator Transitions in Self‐Heated AlxV1−xO2 Single Crystals and Their Visualization

In addition to the well‐known insulator–metal transition above room temperature in pure VO2, AlxV1−xO2 exhibits an insulator–insulator transition at temperatures above room temperature and below the insulator–metal transition temperature, consisting of an increase in resistance by a factor ≤2. The wealth of static and dynamic domain structures discovered in the mixed‐metal‐insulator state of free‐standing, high‐quality, pure VO2 single crystals via optical microscopy synchronous with dc I–V tracing has inspired the use of this technique in these more complex materials. Reported herein are I(V) measurements conducted on crystals of AlxV1−xO2 (0.007≤ × ≤0.02) at various ambient temperatures (To). Prominent features (switching) on the I(V) loops are easily identified with the onset of the insulator–insulator and of the mixed‐metal‐insulator states, both induced by self‐heating (Joule heating). The switching results from instabilities of two different types of negative differential resistance regimes. The applied power at the onset of each switching scales with the excess temperature above ambient. For both transitions, optical microscopy synchronous with dc I–V tracing visualizes the expansion of each phase within the background upon the current increasing, and its contraction upon the current decreasing.

Three-Dimensional Numerical Modeling and Visualization of the Domain Structure in Films with Perpendicular Anisotropy

Three-dimensional numerical modeling of static domain structures in a Co(0001) film is performed for different values of an external magnetic field perpendicular to the surface of the film or lying in the plane of the film. Changes in the fine structure of domain walls, associated with the appearance, motion, and disappearance of Bloch lines and Bloch points, are considered in detail.

Polarized-light and electron microscopy study of the static domain structure of ferroic Fe3B7O13I boracite at room temperature

The static domain structure of ferroic Fe3B7O13I, (abbreviated as Fe-I) synthetic boracite crystals has been analyzed by polarized-light microscopy (PLM) and by field emission scanning electron microscopy (FE-SEM) at room temperature. As for most boracites, Fe-I shows dielectric, elastic, magnetic and optical properties of unusual interest. Upon cooling, Fe-I boracite shows a sequence of structural phase transitions from the cubic -43m to the orthorhombic mm2 (Tc = 348K), the monoclinic m (Tc = 218 K) and the trigonal 3m phases (Tc = 191 K). At room temperature, the Fe-I crystals present an orthorhombic domain structure which consists of six ferroic domains. Our results show that both techniques: PLM and FE-SEM are complementary for the visualization of ferroic domains.

Polarization reversal in lithium niobate using electrodes of dendrite shape created by drying drops of protein-NaCl solution

ABSTRACTWe present a new technique of fabricating the extended-shape electrodes with dendrite channels for formation of the multi-domain state in lithium niobate (LN). The dendrite structure of NaCl created by drying drops of protein-NaCl solution was used for electrode patterning. The linear dependence of the dendrite sizes on drying time has been revealed. The high resolution visualization of the static domain structures created using dendrite electrodes allowed revealing formation of quasi-periodic domain arrays. The produced LN plates with multi-domain regions will be used for manufacturing of the pyroelectric field generators with focusing effect for bioprinting.

Ferroelectricity in Hf0.5Zr0.5O2 Thin Films: A Microscopic Study of the Polarization Switching Phenomenon and Field-Induced Phase Transformations.

Because of their full compatibility with the modern Si-based technology, the HfO2-based ferroelectric films have recently emerged as viable candidates for application in nonvolatile memory devices. However, despite significant efforts, the mechanism of the polarization switching in this material is still under debate. In this work, we elucidate the microscopic nature of the polarization switching process in functional Hf0.5Zr0.5O2-based ferroelectric capacitors during its operation. In particular, the static domain structure and its switching dynamics following the application of the external electric field have been monitored with the advanced piezoresponse force microscopy (PFM) technique providing a nm resolution. Separate domains with strong built-in electric field have been found. Piezoresponse mapping of pristine Hf0.5Zr0.5O2 films revealed the mixture of polar phase grains and regions with low piezoresponse as well as the continuum of polarization orientations in the grains of polar orthorhombic phase. PFM data combined with the structural analysis of pristine versus trained film by plan-view transmission electron microscopy both speak in support of a monoclinic-to-orthorhombic phase transition in ferroelectric Hf0.5Zr0.5O2 layer during the wake-up process under an electrical stress.

Thickness-dependent on the static magnetic properties and dynamic anisotropy of FeNi films with stripe domain structures

FeNi stripe domain (SD) films with broad range of film thicknesses were prepared by electrodeposition method. The static magnetic properties and domain structures as well as the fundamental magnetic parameters of perpendicular anisotropy constant Kp, quality factor Q, critical thickness tc, and domain width w for SD films were studied both from experiment and calculation way respectively. The results showed that the Kp, Q, and w of SD films increased when the film thickness increased. In addition, the thickness dependence of the dynamic properties of FeNi SD films was further studied by a vector network analyzer ferromagnetic resonance. The results indicated a decreased dynamic anisotropy when the films thickness or the applied magnetic field increased. This was related to the enhanced SD structures of film when the thickness increased.

Polarised-Light and Electron Microscopy of the Static Domain Structure of Ferroic Mn3B7O13Br Boracite at Room Temperature

The static domain structure of ferroic Mn3B7O13Br, abbreviated in what follows as Mn-Br, synthetic boracite crystals have been analysed by polarized-light microscopy (PLM) and by field emission scanning electron microscopy (FE-SEM) at room temperature. As most boracites, Mn-Br possess dielectric, elastic, magnetic and optical properties of unusual interest. The stable phase of Mn-Br at room temperature has orthorhombic symmetry (point group mm2) which transforms to a cubic phase (space group ) when heating the crystal above 540 K. Optical examination of all samples grown by chemical transport reactions showed a bulky domain configuration which was resolved in a fine lamellar configuration under the electron microscope.

Ferroelectricity in Si-doped HfO2 revealed: a binary lead-free ferroelectric.

Static domain structures and polarization dynamics of silicon doped HfO2 are explored. The evolution of ferroelectricity as a function of Si-doping level driving the transition from paraelectricity via ferroelectricity to antiferroelectricity is investigated. Ferroelectric and antiferroelectric properties can be observed locally on the pristine, poled and electroded surfaces, providing conclusive evidence to intrinsic ferroic behavior.

Temperature-insensitive large electrostrains and electric field induced intermediate phases in (0.7−x)Bi(Mg1/2Ti1/2)O3–xPb(Mg1/3Nb2/3)O3–0.3PbTiO3 ceramics

Abstract Large electrostrains (∼0.4% at 7 kV/mm) of the new (0.7 − x )Bi(Mg 1/2 Ti 1/2 )O 3 – x Pb(Mg 1/3 Nb 2/3 )O 3 –0.3PbTiO 3 ((0.7 − x )BMT– x PMN–0.3PT) ceramics with x = 0.0–0.7 near the morphotropic phase boundary of the BMT–PT–PMN ternary system were found to be associated with the evolution of the compositionally modulated dielectric relaxor behavior. As disclosed by in situ high-resolution synchrotron X-ray diffraction, more intermediate phases of different symmetries induced by external fields largely contribute to smaller strain hysteresis (∼23%) of PMN-rich compositions than BMT-rich ones. Particularly, the x = 0.2 sample exhibits temperature-insensitive electrostrains of ∼0.3% at 5 kV/mm varying less than 10% from room temperature up to 160 °C, which is mainly attributed to the coexistence of two kinds of relaxor states in a broad temperature range owing to special static domain structures typical for BMT-rich compositions. These findings provide a new approach toward an appropriate compositional design for low-hysteresis temperature-insensitive large electrostrains in BMT-based relaxor ferroelectrics.

Contact Stress-Induced Micromagnetic Behavior in Magnetic Recording Disk

Stress plays an important role in the magnetic properties of ferromagnetic materials. Sliding contact in hard disk drives can lead to tribological failures of the disk in terms of data loss and demagnetization. However, the relationship between contact stress-induced magnetization changes and tribological failures of magnetic recording disk is rarely discussed. In this study, the contact stress-induced micromagnetic behavior in magnetic recording disk was investigated using micromagnetic simulation. A micromagnetic model including the magnetostriction effect into the Landau–Lifshitz–Gilbert equation was developed to simulate the stress effect on the magnetization changes. Then finite element analysis was used to calculate the critical stresses for the occurrence of data loss and demagnetization of perpendicular magnetic recording disk under sliding contact according to our previous experimental results. Based on these simulation results, it was found that the magnetic moment decreased by 8.9 % under the critical stress for data loss, and it rotated 55.7° under the critical stress for demagnetization. In addition, the simulated static domain structures when data loss and demagnetization occur were in agreement with the previously reported experimental results. Finally, the relationship between the contact stress-induced tribological failures and micromagnetic behavior of the magnetic disk was illustrated. It was proposed that data loss is caused by the magnetization reduction, while demagnetization is caused by the magnetization rotation.

Study of Nanoscale Domain Structure and Elastic Response of Lead-Free Piezoelectric Ceramics by Scanning Probe Microscopy

The nanoscale domain structure and variation of local elasticity in lead-free piezoelectric ceramics were investigated using home-made piezoresponse force microscope (PFM) and low-frequency scanning probe acoustic microscope (SPAM) based on a commercial atomic force microscope. The static domain structure and domain dynamics during polarization reversal were studied by PFM, while SPAM investigations showed the elastic and subsurface ferroelectrics structures. PFM and SPAM provided powerful tools for measurements of the local electromechanical and elastic properties of lead-free piezoelectric ceramics.

Piezoresponse force microscopy studies on the domain structures and local switching behavior of Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals

The static domain structures and local switching behavior of relaxor ferroelectric 0.29Pb(In1/2Nb1/2)O3-0.44Pb(Mg1/3Nb2/3)O3-0.27PbTiO3 single crystals at three crystal orientations are studied using piezoresponse force microscopy (PFM). PFM domain imaging shows that both the [001] and [111] oriented crystals exhibit a labyrinth-like surface domain pattern while at the [110] crystal orientation the domains are preferentially aligned along 〈110〉 directions. Vertical and lateral PFM images are used in combination to discuss the polarization vector alignment underlying the observed domain behaviour. Piezoresponse hysteresis loops acquired from these crystals indicate that the [111] crystal orientation has distinct local switching characteristics from the other two orientations in terms of, e.g., coercive voltage. Moreover, we investigate the tip-induced domain growth kinetics on an externally poled [001] crystal, the results of which exemplify an important role of extrinsic factors, e.g., the charge injection effect, in the domain patterning process.

ChemInform Abstract: Viewing Spin Structures with Soft X‐Ray Microscopy

AbstractReview: 102 refs.

Spontaneous Birefringence in Zn3B7O13X Ferroic Boracites

Zn3B7O13Cl and Zn3B7O13Br ferroic boracites were synthesized and their static domain structure and spontaneous birefringence were studied by polarized light microscopy as a function of temperature. The results confirm that the optical indicatrix of the orthorhombic phase in both compositions is biaxial positive type A.

Observation of Ferroelectric Domain Structure in TGS

Triglycine sulfate (TGS) is one of the most intensively investigated ferroelectrics. Though the domain structure is an important subject in the research of ferroelectricity, the domain in TGS is invisible by usual optical method. Many substitutive methods have been developed for the observation of static and dynamic domain structure in TGS. This review summarizes these methods mainly from a practical point of view. The methods referred here are the etching method, the powder deposition technique, the decoration method, the nematic liquid crystal (NLC) method, the scanning electron microscopy (SEM), the pyroelectric probe technique (PPT), the X-ray diffraction microscopy, the cleavage method, the scanning probe microscopy (SPM) and others.

Magnetic force microscopy investigation of the static magnetic domain structure and domain rotation in Fe-x at. %Ga alloys

Magnetic domain structures and domain rotation process in Fe-x at. %Ga (x=12, 19, and 25) alloys have been studied by magnetic force microscopy. Our results show that the missing connection between magnetic domains and the underlying microstructure [Xing and Lograsso, Appl. Phys. Lett. 93, 182501 (2008)] is (i) a perpendicular magnetic anisotropy; and (ii) domain irregularities/fluctuations induced by a quenched random-field condition: both of which may have direct relations with dispersed low-symmetry nanoprecipitates [Cao, et al., Phys. Rev. Lett. 102, 127201 (2009)].

The Spectrum of Magnetostatic Waves in Ferromagnetic with Moving Periodical Domain Structure

The spectral properties of magnetostatic waves in a ferromagnet with a moving periodic domain structure are studied within the exchange-free magnetostatic approximation. It is demonstrated that the Doppler frequency shift caused by the domain-wall motion results in the splitting of the spectrum of each magnetostatic wave mode into two dispersion branches―high-frequency and low-frequency branches. It is found that the more the mode number, the more the separation between these branches with respect to the mode spectrum in the presence of the static domain structure. PACS numbers: 75.60.-d, 75.60.Ch, 75.70.Kw

Effect of Sawtooth Shape on Switching Process of Write Head

The static states and reversal processes of write head are studied and compared by two micromagnetic models with sawtooth edges or smooth edges, respectively. In the calculation of magnetostatic interaction with smooth edges, the analytical expression of demagnetization matrix for right-angle triangular prism clusters at hypotenuse has been found. The static domain structures in the main pole tip of both models have a slight difference and differ a little more with higher exchange constant. The switching processes in the two models also have similar behavior, except when the down-track film thickness is less than the pole tip width. Both the exchange field and film thickness affect the ultimate magnetization perpendicular to media and the speed of reversal.