The dimensions of magnetized devices used in spintronics are so small that thermal fluctuations are allowed to play a significant role in their magnetization dynamics. Nowadays, the term “spin caloritronics” was coined to refer to all transport phenomena that involve both spin and heat [1]. However, what was not already anticipated is that the fluctuations, described by a stochastic thermal bath, interacts with the magnetic degrees of freedom, namely, spins, in a way to generate effective motions, that changes the nature of their dynamics. The quantities of interest become correlation functions of the magnetization instead, which can be deduced from numerical simulations or measured by dedicated experiments. In this talk I present how a systematic statistical averaging procedure, based on functional calculus, can be applied to the derivation of sets of effective equations for the moments of the spin variables. This approach differs quite significantly from previous attempts where the form of the equilibrium distribution, for instance, is not postulated, but is deduced from the evolution of the off-equilibrium dynamics of equal-time correlation functions [2], instead. I show that, thanks to “Formulae of differentiation”, many forms of interacting systems can be deduced that connect tightly both the motion of magnetic moments to the fluctuations of the bath itself [3,4]. This may open new paradigms for spin caloritronics experiments.
[1] H.Yu et al, Physics Letters A 381, 825 (2017)
[2] J.Tranchida, P.Thibaudeau and S.Nicolis, Phys.Rev.E 98, 042101 (2018)
[3] J.Tranchida, P.Thibaudeau and S.Nicolis, Physica B 486, 57 (2016)
[4] P.Thibaudeau, J.Tranchida and S.Nicolis, IEEE Trans.Mag. 52, 1300404 (2016)
Plus d'information :
https://www.spintec.fr/seminar-spinning-in-a-bath-thermal-handshakes-of-rotating-particles/