Author Archives: ezeferrero@gmail.com

Our article “Magnetic domain wall creep and depinning: A scalar field model approach” is now published in PRE

Magnetic domain wall motion is at the heart of new magnetoelectronic technologies and hence the need for a deeper understanding of domain wall dynamics in magnetic systems. In this context, numerical simulations using simple models can capture the main ingredients responsible for the complex observed domain wall behavior. We present a scalar field model for the magnetization dynamics of quasi-two-dimensional systems with a perpendicular easy axis of magnetization which allows a direct comparison with typical experimental protocols, used in polar magneto-optical Kerr effect microscopy experiments. We show that the thermally activated creep and depinning regimes of domain wall motion can be reached and the effect of different quenched disorder implementations can be assessed with the model. In particular, we show that the depinning field increases with the mean grain size of a Voronoi tessellation model for the disorder.

Phys. Rev. E 97, 062122 – Published 11 June 2018
https://journals.aps.org/pre/abstract/10.1103/PhysRevE.97.062122

 

Our article “Damage accumulation in silica glass nanofibers” to appear in Nano Letters

The origin of the brittle-to-ductile transition, experimentally observed in amorphous silica nanofibers as the sample size is reduced, is still debated. Here we investigate the issue by extensive molecular dynamics simulations at low and room temperatures for a broad range of sample sizes, with open and periodic boundary conditions. Our results show that small sample-size enhanced ductility is primarily due to diffuse damage accumulation, that for larger samples leads to brittle catastrophic failure. Surface effects such as boundary fluidization contribute to ductility at room temperature by promoting necking, but are not the main driver of the transition. Our results suggest that the experimentally observed size-induced ductility of silica nanofibers is a manifestation of finite-size criticality, as expected in general for quasi-brittle disordered networks.

A nice collaboration with Silvia Bonfanti, Alessandro Sellerio, Roberto Guerra and Stefano Zapperi at CC&B Milano.
A ‘Just-Accepted’ version of the manuscript can be found here.

Magnetic domain wall creep and depinning: a scalar field model approach

Our new preprint on magnetic domain wall creep and depinning is available online!!!

Researcher position

I have started a new fresh year in a new office and a new desk, this time as an stable researcher of CONICET (the Argentinean National Research Council). I’m joining a group of excellent people, the condensed matter theory group, at Centro Atómico Bariloche (Argentina), a great spot to do science. I’m grateful to the group for the welcoming and to all my previous hosts for a very soft and enriching postdoc path to my actual position. Thanks!

Centro Atómico Bariloche (some time ago)

Visit to Segrate

Last November 17th I had the pleasure of present a seminar at Dipartimento di Biotecnologie Mediche e Medicina Traslazionale, UNIMI, in Segrate, Italy. I was surprised by the amount of people that showed up in the room and participated in the discussion. I’m thankful to Fabio Gavazzi and Roberto Cerbino for their invitation and warm welcome.

Third workshop of CC&B – 9 Oct Milano

Happy to be part of the third workshop of the Center for Complexity & Biosystems, University of Milan, with a broad interdisciplinary scope.

Review article: Deformation and flow of amorphous solids: a review of mesoscale elastoplastic models

It has been a very long work, beautifully leaded by Alexandre the great, but finally it’s out there: the preprint of our review article on elastoplastic models for the deformation of amorphous solids. Since we begin a long edition path now, any comments and suggestions would be welcome! Enjoy! (arxiv:1708.09194)

Coming back from Advances in Complex Systems (Lake Como School of Advanced Studies)

Last week has been full of nice discoveries at LCSAS . Physics has still a lot to say about biological systems. Thanks to Stefano Zapperi, Caterina La Porta and Mikko Alava for bringing together some great speakers and given us the opportunity to participate.

 

My visit to Naples!

I had had the pleasure to be in Napoli giving a seminar at the Physics Department of the University of Naples Federico II, followed by very interesting discussions with colleagues that showed up for the occasion. I would like to thank all of them and specially my host in this visit and good friend Raffaele Pastore for such a wonderful time in the adoptive city of Diego Armando 🙂 .

Our article “Spatiotemporal patterns in ultraslow domain wall creep dynamics” published in PRL

(edited) Our article is now available online in Phys. Rev. Lett. !

In presence of impurities, ferromagnetic and ferroelectric domain walls slide only above a finite external field. Close to this depinning threshold, they proceed by large and abrupt jumps, called avalanches, while, at much smaller field, these interfaces creep by thermal activation. In this work we develop a novel numerical technique that captures the ultra-slow creep regime over huge time scales. We point out the existence of activated events that involve collective reorganizations similar to avalanches, but, at variance with them, display correlated spatio-temporal patterns that resemble the complex sequence of aftershocks observed after a large earthquake. Remarkably, we show that events assembly in independent clusters that display at large scales the same statistics as critical depinning avalanches. We foresee this correlated dynamics being experimentally accessible by magneto-optical imaging of ferromagnetic films.