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Depinning Olympics [paper and game!]

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A one dimensional elastic string driven by a uniform force in a random medium is a minimal model for a field driven domain wall in a large family of thin-film ferromagnetic materials.  The motion of the elastic string at zero temperature is characterized by a depinning threshold fc , such that if the driving is f<fc the string is blocked after a transient, while for f>fc it slides and never stops, acquiring a well defined and finite steady-state average velocity. At finite temperature, thermal activation allows the string to have a finite average velocity at all finite driving forces however. As a result, the mean velocity is an interesting function v(T,f) which presents a creep regime for f<fc , a depinning region for f>~fc , and a flow regime for f>>fc . The depinning transition was recently characterized experimentally by L. J. Albornoz et al. in thin-film ferrimagnets at very low temperatures. Now it is your turn to find a depinning transition! The applet ...
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Universal critical exponents of the magnetic domain wall depinning transition [paper]

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PRB Letter  Universal critical exponents of the magnetic domain wall depinning transition  L. J. Albornoz, E. E. Ferrero, A. B. Kolton , V. Jeudy, S. Bustingorry, and J. Curiale Phys. Rev. B 104, L060404 – Published 5 August 2021 Magnetic-field-driven domain wall dynamics in a ferrimagnetic GdFeCo thin film with perpendicular magnetic anisotropy is studied using low-temperature magneto-optical Kerr microscopy. Measurements performed in a practically athermal condition allow for the direct experimental determination of the velocity ( β = 0.30 ± 0.03 ) and correlation length ( ν = 1.3 ± 0.3 ) exponents of the depinning transition. The whole family of exponents characterizing the transition is deduced, providing evidence that the depinning of magnetic domain walls is better described by the quenched Edwards-Wilkinson universality class. Experimental Results Domain Wall velocity-field characteristics and avalanche correlation length 
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Curvature-driven ac-assisted creep dynamics of magnetic domain walls [paper]

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  PRB Letter   P. Domenichini, F. Paris, M. G. Capeluto, M. Granada, J.-M. George, G. Pasquini, and A. B. Kolton Phys. Rev. B 103, L220409 – Published 24 June 2021 The dynamics of micrometer-sized magnetic domains in ultrathin ferromagnetic films is so dramatically slowed down by quenched disorder that the spontaneous elastic tension collapse becomes unobservable at ambient temperature. By magneto-optical imaging we show that a weak zero-bias ac magnetic field can assist such curvature-driven collapse, making the area of a bubble to reduce at a measurable rate, in spite of the negligible effect that the same curvature has on the average creep motion driven by a comparable dc field. An analytical model explains this phenomenon quantitatively. Experiment Interactive Simulation of a time dependent phi4 model
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