Universal dimensional crossover of domain wall dynamics in ferromagnetic films

Torres, W. Savero; Pardo, R. Díaz; Bustingorry, Sebastián; Kolton, Alejandro B.; Lemaı̂tre, A.; Jeudy, V.

doi:10.1103/physrevb.99.201201

Cited by 12 publications

(10 citation statements)

References 27 publications

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“…Therefore, in a one-dimensional interface, the theoretically found equilibrium roughness exponent ζ = 2/3 25,26 implies a creep exponent µ = 1/4. This value of the creep exponent has been corroborated in many experiments 21,22,27,28 . However, the experimental determination of the roughness exponent ζ is challenging and, while it can be computed in different ways 12,21,22,[28][29][30][31] , there is a wide spread in the reported values [29][30][31][32] .…”

Section: Introductionsupporting

confidence: 73%

“…This value of the creep exponent has been corroborated in many experiments 21,22,27,28 . However, the experimental determination of the roughness exponent ζ is challenging and, while it can be computed in different ways 12,21,22,[28][29][30][31] , there is a wide spread in the reported values [29][30][31][32] . Furthermore, besides the equilibrium roughness exponent, the morphology can be described with different roughness exponents at different length scales 18,33,34 , which prompt to a careful interpretation of the experimentally found values 35 .…”

Section: Introductionsupporting

confidence: 73%

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Transient magnetic-domain-wall ac dynamics by means of magneto-optical Kerr effect microscopy

et al. 2019

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The domain wall response under constant external magnetic fields reveals a complex behavior where sample disorder plays a key role. Furthermore, the response to alternating magnetic fields has only been explored in limited cases and analyzed in terms of the constant field solution. Here we unveil phenomena in the evolution of magnetic domain walls under the application of alternating magnetic fields within the creep regime, well beyond a small fluctuation limit of the domain wall position. Magnetic field pulses were applied in ultra-thin ferromagnetic films with perpendicular anisotropy, and the resulting domain wall evolution was characterized by polar magneto-optical Kerr effect microscopy. Whereas the DC characterization is well predicted by the elastic interface model, striking unexpected features are observed under the application of alternating square pulses: magneto-optical images show that after a transient number of cycles, domain walls evolve toward strongly distorted shapes concomitantly with a modification of domain area. The morphology of domain walls is characterized with a roughness exponent when possible and contrasted with alternative observables which result to be more suitable for the characterization of this transient evolution. The final stationary convergence as well as the underlying physics is discussed.

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Section: Introductionsupporting

confidence: 73%

Section: Introductionsupporting

confidence: 73%

Transient magnetic-domain-wall ac dynamics by means of magneto-optical Kerr effect microscopy

et al. 2019

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“…Though knowing the roughness exponent is necessary for a complete understanding of domain-wall dynamics, after the work of Lemerle and coworkers [27] experimental reports of roughness exponents of domain walls in magnetic thin films are scarce (see Refs. [9,[29][30][31][32][33][34][35][36]). Measuring domainwall roughness exponents would require to experimentally obtain domain-wall positions and then to define and compute a proper correlation function, such as the commonly used roughness function B(r), which measures displacementdisplacement correlations.…”

Section: Introductionmentioning

confidence: 99%

Statistically meaningful measure of domain-wall roughness in magnetic thin films

et al. 2020

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Domain walls in magnetic thin films display a complex dynamical response when subject to an external drive. It is claimed that different dynamic regimes are correlated with the domain-wall roughness, i.e., with the fluctuations of domain-wall position due to the inherent disorder in the system. Therefore, key to understanding the dynamics of domain walls is to have a statistically meaningful measure of the domain-wall roughness. Here we present a thorough study of the roughness parameters, i.e., roughness exponent and roughness amplitude, for domain walls in a ferrimagnetic GdFeCo thin film in the creep regime. Histograms of roughness parameters are constructed with more than 40 independent realizations under the same experimental conditions, and the average values and standard deviations are compared in different conditions. We found that the most prominent feature of the obtained distributions is their large standard deviations, which is a signature of large fluctuations. We show that even if the roughness parameters for a particular domain wall are well known, these parameters are not necessarily representative of the underlying physics of the system. In the low field limit, within the creep regime of domain-wall motion, we found the average roughness exponent and roughness amplitude to be around 0.75 and 0.45 μm 2 , respectively. When an in-plane magnetic field is applied we observed that, even though the distributions are wide, changes in the mean values of roughness parameters can be identified; the roughness exponent decreasing to values around 0.72 while the roughness amplitude increases to 0.65 μm 2. Our results call for a careful consideration of statistical averaging over different domains walls when reporting roughness exponents.

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“…Diverse systems including ferroic domain walls [1][2][3][4][5][6][7][8][9][10][11], cell fronts [12,13], bacterial colonies [14], or contact lines [15] exhibit emergent structures separating different "states" or domains (i.e., different magnetization orientations in the case of ferromagnetic systems, or different polarization orientations in the case of ferroelectrics, or cells-media in cell fronts, or wet from dry in the case of contact lines), usually called interfaces. From a technological point of view, controlling interfaces is of great interest for various reasons.…”

Section: Introductionmentioning

confidence: 99%

From bulk descriptions to emergent interfaces: Connecting the Ginzburg-Landau and elastic-line models

et al. 2020

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Controlling interfaces is highly relevant from a technological point of view. However, their rich and complex behavior makes them very difficult to describe theoretically, and hence to predict. In this work, we establish a procedure to connect two levels of descriptions of interfaces: for a bulk description, we consider a two-dimensional Ginzburg-Landau model evolving with a Langevin equation, and boundary conditions imposing the formation of a rectilinear domain wall. At this level of description no assumptions need to be done over the interface, but analytical calculations are very difficult to handle, especially for disordered systems. On a different level of description, we consider a one-dimensional elastic line model evolving according to the Edwards-Wilkinson equation, which only allows one to study continuous and univalued interfaces, but which was up to now one of the most successful tools to treat interfaces analytically. To establish the connection between the bulk description and the interface description, we propose a simple method which has the advantage to be readily applicable to disordered systems. We probe the connection by numerical simulations at both levels for clean and disordered systems, and our simulations, in addition to making contact with experiments, allow us to test and provide insight to develop new analytical approaches to treat interfaces.

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Universal dimensional crossover of domain wall dynamics in ferromagnetic films

Cited by 12 publications

References 27 publications

Transient magnetic-domain-wall ac dynamics by means of magneto-optical Kerr effect microscopy

Transient magnetic-domain-wall ac dynamics by means of magneto-optical Kerr effect microscopy

Statistically meaningful measure of domain-wall roughness in magnetic thin films

From bulk descriptions to emergent interfaces: Connecting the Ginzburg-Landau and elastic-line models

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