Seminar – Entropic effects and solitons in thermally activated magnetic transitions

On Wednesday, March 9th at 11:00 Louise Desplat from Université de Liège will give us a seminar entitled:
Entropic effects and solitons in thermally activated magnetic transitions

Place : CEA Bat. 10.05 Room 445 (limited to persons having a CEA Badge)
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Abstract: The rate of thermally activated transitions can generally be described by the Arrhenius law, as k=f0 exp(-βΔE), in which is the energy barrier, and f0 is a prefactor. Within the magnetic community, it is common practice to assume a constant value of f0 as a characteristic frequency of the dynamics – typically a few GHz, and focus on the barrier to assess thermal stability of magnetic textures. In this work, we show how the activation entropy contained in the prefactor can play a crucial role in thermally activated magnetic transitions. By means of atomistic simulations, we demonstrate entropic narrowing for skyrmions, whereby the activation entropy tends to stabilize an isolated skyrmion against the collinear ground state. For the free layer of a magnetic tunnel junction, we shed light onto the Meyer-Neldel compensation phenomenon, in which fluctuations favour the domain wall configuration at the saddle point, over the stable collinear state, thereby drastically reducing information retention times in memory applications.
Desplat et al., PRB 98, 134407 (2018)
Desplat et al., PRB 101, 060403(R) (2020)
Desplat and Kim, PRL 125, 107201 (2020)
Desplat and Kim, Phys. Rev. Appl. 14, 064064 (2020)

Biography : After a Masters’ degree in Condensed Matter and Nanophysics from the University of Strasbourg, Louise Desplat obtained her PhD from the University of Glasgow, UK, on thermal stability of metastable magnetic skyrmions, under the co-supervision of Robert Stamps and Joo-Von Kim at C2N/UP-Saclay. She then did a two-year Postdoc at the University of Strasbourg, working with Bertrand Dupé and Paul-Antoine Hervieux on electric-field skyrmion control. She has recently began a two-year Postdoc fellowship at the University of Liege in the Nanomat group of Matthieu Verstraete and Bertrand Dupé, to work on multiferroic skyrmions.

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