Alternating superlattice textures in driven nanomagnets

Abstract

Nanomagnets driven with uniform electric currents exhibit a wide variety of spatial textures. In the present work, we investigate alternating superlattice states in nanomagnets, which are spatially periodic textures composed by several spatial modes that oscillate in time. The magnetic system is described in the continuum approach by the Landau–Lifshitz–Gilbert–Slonczewski equation, and direct numerical simulations of this model allow us to characterize the alternating patterns. As a result of this temporal oscillation, textures alternate between different shapes. In particular, we focus on two types of textures, namely a superhexagon and a square-like pattern, which are composed by six and two dominant Fourier modes, respectively. Based on an appropriate modal decomposition, we reveal that the mechanism that originates the alternating superhexagon is a homoclinic bifurcation. In addition, we show that the oscillatory square-like texture emerges through a supercritical Andronov–Hopf bifurcation.