Welcome to the next PoreLab lecture!
Who: Prof. Gloria Maria Buendia from the department of Physics at Universidad Simón Bolívar, Caracas in Venezuela
When: Wednesday 4 September at 13:00 (Norway time).
Where: The lecture will be in-person in the Kelvin room (PoreLab Oslo) and will be streamed in the common room (PoreLab Trondheim). From anywhere else, you will be able to join via the following Zoom link:
https://uio.zoom.us/j/65837085049?pwd=WjZianUyN3FJa2liQkxBbzQrOCtGdz09
Title: Novel non-equilibrium behavior of spin systems: experiments and simulation match
Abstract: Dynamical and thermal phase transitions of classical spin systems belong to the same universality class. But recent experiments {P. Riego , P. Vavassori, A. Berger, Phys.Rev.Lett. 118, 117202 (2017)}, show that when thin Co films are subjected to a slow enough periodical sinusoidal field plus a constant one (bias), they present metamagnetic anomalies. These anomalies appear in the form of two symmetrical peaks with respect to zero bias, in the susceptibility and in the scaled variance curves. This behavior has no analog in the equilibrium model, and at first it was considered to be due to a critical phenomenon or to a residual magnetization. However, numerical and experimental studies clearly indicate that they have a different origin. In this work we go through a detailed Monte Carlo calculation on the S=1/2 Ising and the S=1 Blume-Capel models that demonstrates that the observed anomalies are due to a stochastic phenomenon associated with a change in the decay mechanism toward the stable phase. For weak bias fields the decay occurs by a deterministic multidroplet mechanism, while for larger bias fields it occurs by a single-droplet mechanism. As we show by applying nucleation theory this change is due to the dependence of the droplet size on the applied field.