Controlling the preferred direction of the magnetic moments is essential for the design of spintronic devices based on ultrathin films and heterostructures. As the film thickness or the temperature is increased, the easy anisotropy axis is typically reoriented from an out-of-plane direction preferred by surface and interface energy contributions to an in-plane alignment favored by the volume anisotropy terms, termed a spin-reorientation transition (SRT). In this talk I will first discuss the well-tempered metadynamics, the method we used for the simulations, as well as ab initio methods to calculate the parameters of the spin model. Then I will present our results on Fe bilayers deposited on Au(001) substrate and show theoretical evidence for the temperature dependent SRT in Fe bilayers on W(110) [1]. In context of this sytem, I will finally outline the importance of the Dzyaloshinsky-Moriya interactions in the emergence of the SRT [2].

[2] B. Nagyfalusi, L. Udvardi, L. Szunyogh, and L. Rózsa, arxiv:2007.14116 (2020)