Spin polarization in an ac-driven magnetic material with vanishing net magnetization: a new proposal

Abstract

In this work, we address the fundamental question of whether a magnetic material having zero net magnetization can produce polarized spin current from a completely unpolarized one. Common wisdom suggests that this is not possible, but if we break the symmetry in hopping integrals in different segments of the magnetic sample, then a finite possibility of getting polarized spin current is established. To substantiate this fact, we consider a one-dimensional magnetic chain with vanishing net magnetization where one part of the chain is subjected to an ac electric field, keeping the other part free. The ac field, introduced through Peierls substitution, modulates the hopping integrals yielding a misalignment of up and down spin channels, which is the primary requirement to get finite spin polarization. Simulating the system within a tight-binding framework, we compute spin-dependent transmission probabilities using the well-known Green’s function prescriptionand determine junction currents following the Landauer–Büttiker formalism. Our analysis may shed some light on designing spin-polarized devices using driven magnetic materials with vanishing net magnetization.