Response Of Domain Walls Research Articles

Detection of paired domain walls in a ferromagnetic ring by a bend resistance measurement

We have investigated dynamics of paired domain walls in a microfabricated ferromagnetic ring by using a ballistic transport character of a two-dimensional electron gas (2DEG) microcross. The stray field from the domain walls results in a change in the bend resistance of the 2DEG cross lying beneath the ferromagnetic ring depending on the positions of the domain walls. The measurements for different directional angles of the applied magnetic field reveal that the domain wall behavior is strongly affected by identical local defects in the ring. We have also studied a response of paired domain walls under a pulsed magnetic field. We find that the paired domain walls switch the positions without annihilation under a pulsed magnetic field with a short rise time.

Domain wall induced modes of high-frequency response in ferromagnetic elements

The influence of domain wall density on the magnetization dynamics of amorphous CoZrTa thin-film elements was investigated by a combination of microwave magnetometry and quasistatic plus time-resolved wide-field Kerr microscopy. In addition to domain wall motion, permeability rolloff at low frequencies occurs due to rotational processes. The dominating ferromagnetic resonance modes depend on the domain wall density due to the formation of a zone of magnetization curling at the domain walls, which results from a phase lag of domain and domain wall response. Both the amount of permeability reduction and the increase in precessional frequency, can be varied with magnetic history. All effects are avoided by lamination of the ferromagnetic films. The results demonstrate the importance of detailed domain control for the optimization of patterned films for high-frequency applications, beyond the elementary adjustment of material’s high-frequency properties.

Diffuse phase transition in BaTi1−xSnxO3 ceramics: An intermediate state between ferroelectric and relaxor behavior

Dielectric relaxation and polar structures of BaTi1−xSnxO3 ceramics, x=0.10–0.20, are investigated by means of dielectric spectroscopy and piezoresponse force microscopy. A transition regime between “normal” ferroelectric and relaxor behaviors is encountered. In the compositions with x=0.10, a complex domain pattern confirming the ferroelectric state is observed. Strong dielectric relaxation around Tm is attributed to domain wall motion. On the other hand, the dielectric spectra in the sample with x=0.20 are very similar to those observed in relaxor ferroelectrics. Analysis of the relaxation spectra at the intermediate concentration, x=0.15, reveals both domain wall response and an additional contribution related to mesoscale polar structures. The appearance of relaxor behavior in BaTi1−xSnxO3 is discussed within the framework of the random field model.

Quantum Phase Transition and Dielectric Domain Wall Response of SrTi18O3

The complex susceptibility of SrTi18O3 (STO18) has been measured at frequencies 10−3 < f < 105 Hz and temperatures 5 < T < 90 K with ac field amplitudes 10 < E0 < 300 V/m in order to inspect the phase transition and its quantum nature, and to study the dielectric dispersion and loss of the “unknown” dipolar defects involved in the dielectric spectra at low temperatures. The phase transition turns out to be of second order, but slightly smeared and to possess mean-field quantum behavior. The dipolar defects are proposed to be due to V0 centers coupled to adjacent Ti3+ ions (trapped small polarons). Owing to their random charge nature they are assumed to be responsible for the random field-controlled domain wall response. At frequencies above their dipolar relaxation step they act as strong pinning centers involving frozen dipolar fields, which completely suppress any domain wall response to low driving fields E0.

Phase transition and random-field induced domain wall response of SrTi O 3

The dielectric permittivity e′ - i\(\) of SrTi 18O 3 (STO18) is studied under a dc electric field E as a function of the temperature, T. In e′vs.T, a double-peak is found when 0 < E < 30 KV/m. While the peak at high-T is attributed to the smeared ferroelectric phase transition, the low-T one is induced by domain wall motion. The transverse Ising model including an external homogeneous and quenched random-fields is successfully used to describe both the smeared phase transition and the domain wall response in the low-T domain state. The calculations are in good agreement with the experimental results.

Dielectric study of purified Rb2ZnCl4 in weak ac-fields

The strongly enhanced domain wall response in the ferroelectric phase of purified Rb2ZnCl4 is studied at low ac-field level E(ac)≤0.3V/cm. In the incommensurate-commensurate transition range, the thermal hysteresis of the imaginary part ϵ″(T) of permittivity is much bigger than those of ϵ′(T). At low frequencies, an anomaly of ϵ″(T) is observed at T≈170K.

Nonlinear ferroelectric domain wall response

The ac-field dependence of complex dielectric coeffcients in the improper ferroelectric phase of incommensurate Rb2ZnCl4 crystals is analyzed and compared with those observed in donor doped lead zirconate titanate (PZT) piezoceramics. For all coefficients examined, a threshold field for the onset of nonlinearity exists leading to qualitatively the same non-analytic scaling behavior above threshold. Due to the similar nonlinear behavior of very different ferroelectric systems, we suggest that a universal mechanism may exist in a larger class of ferroelectrics causing nonlinearity at moderate field level. This may be related to the dynamics of randomly pinned elastic interfaces driven at field strengths slightly above threshold for collective interface motion.

A micromagnetic model domain wall resonance in thin films

Domain wall and ferromagnetic resonances in perpendicularly magnetised ferromagnetic thin films are studied using a numerical time dynamic micromagnetic method. The dynamic response of Bloch domain walls in stripe domain patterns is examined for different orientations of a static applied field. The calculations are in good agreement with recent experimental results.

Threshold of irreversible domain wall motion in soft PZT-piezoceramic

The nonlinear ac-field dependence of dielectric and piezoelectric coefficients in soft PZT piezoceramics is studied at f= 100Hz. We demonstrate that two different thresholds for the onset of nonlinearity exist at Ec2 ≈ 1 V/cm and Ec1 ≈ 100 V/cm, respectively. At weak fields, the ac-field dependence of the effective dielectric coefficients obeys a scaling law x=xo + A[(E-Ec)/Ec] with the effective coefficient φ = 1.5 ± 0.1. Above the large field threshold, both dielectric and piezoelectric coefficients exhibit a non-analytic scaling behavior. The nonlinearity is here anisotropic which is reflected by exponents φ = 1.0 ± 0.1 and φ = 1.2 ± 0.1 for fields parallel and perpendicular to the poling direction of the ceramic, respectively. The nonlinear domain wall response at fields well below the electrical depoling field is apparently dominated by the depinning of domain walls rather than by the anharmonicity of the potential energy of the wall.

Domain wall relaxation in purified Rb2ZnCl4-crystals

Abstract We have studied the frequency dependent domain wall response in the lock-in phase of purified RZC crystals. Our investigations carried out at low measuring fields reveal for the first time a pronounced temperature hysteresis of the relaxation time τ in the interval 193 K > T > 170 K and a steep increase of τ on cooling below T = 165 K.

Dynamic response of domain walls on the air-bearing surface of thin-film heads

The domain configurations on the air-bearing surface (ABS) of inductive thin-film recording heads were studied. It was found that, instead of being a single domain structure, the ABS of a thin-film head usually has multidomains. The direction of the domain walls is neither parallel nor perpendicular to the gap plane. The magnetization was found to be in the plane of the ABS along the track width, with the magnetizations on the two sides of the domain walls either ‘‘head-to-head’’ or ‘‘tail-to-tail.’’ The domain walls are slanted in order to spread the magnetic charges along the wall over a larger region, thereby reducing magnetostatic energy in this configuration. The responses of the domain walls are not all in phase, and they are generally out of phase with the rotational process along the gap edge. The magnetization configuration on the ABS and in the throat and the sloped region were investigated in one head and correlated with the domain walls on the ABS.

Toward a better theory of thermal remanent magnetization

The major results of this paper are the pointing out of deficiencies in existing thermal remanent magnetization theories for nonuniformly magnetized grains and the suggestion of ways in which some of these deficiencies might be removed. Most models of pseudo single domain behavior fail to predict certain critical experimental observations of TRM, particularly those dealing with magnetic stability. At least part of the problem with understanding TRM in small nonuniformly magnetized grains is that the size and role of the demagnetization field has been grossly overestimated. TRM in small multidomain grains is probably acquired by domain wall movement, except for the smallest (submicron) grains in which pseudo single domain behavior associated with wall moments probably dominates. A collective response of domain walls seems to be required to explain magnetic stability observations, although the degree and the precise nature of this collective response has not yet been determined.

Generalized susceptibility of a solitary wave

We define a generalized susceptibility for solitary wave solutions of the nonlinear Klein–Gordon equation and obtain its expression in terms of the complete set of functions which arise in the linear stability analysis of the solitary wave. Explicit expressions are presented for the susceptibility of the sine-Gordon soliton and the φ4 kink. Plots are presented for the long-wave dynamic polarizability of the φ4 kink which have application to the response of ferroelectric domain walls to an oscillating external electric field.

Stroboscopic observation of magnetic domain wall motion in yttrium orthoferrite for the region of Walker's critical velocity

The response of magnetic domain walls in yttrium orthoferrite (YFeO3) to a pulsed driving field was observed by a stroboscopic technique. The results demonstrate that the present technique is very useful for the observation of high-speed domain wall motion, and is capable of achieving a time resolution of less than a few nanoseconds. Some interesting responses, eg high speed shrinkage of narrow strip domains, domain annihilation, and critical velocities were found in this experiment. The observed maximum velocity of the domain wall was higher than the Walker's critical velocity of YFeO3 (about 3·6×105 cm s−1) predicted by Hagedorn. Moreover, critical-velocity-like responses were found at two velocities, about 4·5×105 cm s−1 and about 7·7×105 cm s−1. A critical-velocity-like motion of about 6·5×105 cm s−1 was found for the motion of the tip of narrow strip domains during pulsed field driving.

Response of magnetic domain walls to ultrasound

physica status solidi (a)Volume 25, Issue 1 p. K9-K11 Short Note Response of magnetic domain walls to ultrasound O. Bostanjoglo, O. Bostanjoglo Optisches Institut der Technischen Universität Berlin Search for more papers by this author O. Bostanjoglo, O. Bostanjoglo Optisches Institut der Technischen Universität Berlin Search for more papers by this author First published: 16 September 1974 https://doi.org/10.1002/pssa.2210250138Citations: 1 Bereich: ehemaliges I. Physikalisches Institut. AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Citing Literature Volume25, Issue116 September 1974Pages K9-K11 RelatedInformation

The dynamic response of magnetic domain walls to applied fields in yttrium orthoferrite, observed by a stroboscopic technique

The dynamic response of magnetic domain walls to applied fields in yttrium orthoferrite grown by the flux method was observed by using a light-emitting diode as a stroboscopic light source. The observed relation between strip domain width and time is not a simple exponential function as calculated from a simple relaxation model, but is more complicated, having two different regions of response time. The estimated relation of domain wall velocity with drive field indicates a remarkable nonlinear behaviour, and this is consistent with results observed by the bubble collapse method previously reported by the authors. Two critical velocities, about 4000-5000 cm s−1 and about 150 cm s−1, were confirmed in the present experiment.

Stroboscopic Observation of Magnetic Domain Wall Motion with a Light Emitting Diode

A simple stroboscopic apparatus using a light emitting diode as a light pulse source is described for the observation of dynamic response of domain walls under high speed magnetic pulse field.

Dynamic ferromagnetic domain wall response to incremental AF fields and Becker wall area measurement technique

Dynamic ferromagnetic domain wall response to incremental AF fields and Becker wall area measurement technique

Magnetoresistance and Magnetic Switching in Permalloy Films

Magnetoresistance measurements have been used to study the magnetic properties of Permalloy films. Resistivities parallel and transverse to the current were measured simultaneously as the applied magnetic field was varied in magnitude or direction in the film plane. The results are discussed in terms of a representation in which the resistivity components are regarded as Cartesian coordinates. This representation is independent of the current direction relative to any magnetically preferred orientations in the film. The statistical,domain-wall, switching model of Conger and Essig is extended to include the situation in which the field and easy magnetic axis are not parallel, and a switching profile is constructed which gives a unified representation of the domain wall and coherent rotational switching response of a uniaxial film to an applied field. The incidence of moving domain walls under certain field conditions is discussed with the help of this profile,and it is shown that the magnetoresistance curves may be understood in terms of the magnetic changes.