Speaker
Description
In recent years, artificial spin systems, consisting of elongated single-domain ferromagnetic nanomagnets placed on the nodes of two-dimensional lattices and coupled via their dipolar magnetic fields, have been used to address open questions in frustrated magnetism. However, the imaging techniques so far used, are severely constrained in time and spatial resolution. We have therefore recently developed x-ray resonant scattering to probe the magnetic configuration in artificial spin systems, which allows us to go beyond these limits in time and spatial resolution, and provide a means to determine, for example, the predicted phase transitions in artificial spin systems. As a result, we have been able to measure magnetic correlations in a highly dynamic artificial kagome spin ice with sub-70 nm Permalloy nanomagnets [1].
In this contribution, I will illustrate our recent results that establish the critical properties of the antiferromagnetic phase transition in artificial square ice composed of superparamagnetic nanoelements with fluctuating magnetic moments, showing that it belongs to the two-dimensional Ising universality class [2]. In addition, taking advantage of the flexibility in the design of the magnetic properties of our system, we have determined the influence of the proximity of the blocking temperature relative to the phase transition temperature, resulting in a dramatic change on the out-of-equilibrium dynamics due to critical slowing down at the phase transition.
[1] O. Sendetskyi, et al. Phys. Rev. B 93, 224413 (2016)
[2] O. Sendetskyi, et al. (under review)
