Laser-induced helicity and texture-dependent switching of nanoscale stochastic domains in a ferromagnetic film

TL;DR

This study demonstrates that circularly polarized picosecond laser pulses can induce nanoscale magnetic domain textures in a ferromagnetic film, with effects depending on laser helicity and domain texture, revealing a new ultrafast control mechanism.

Contribution

It introduces a novel method for controlling nanoscale magnetic textures using laser helicity and texture-dependent effects, supported by a stochastic nucleation model.

Findings

Laser pulses induce stochastic nucleation of magnetic domains.

Domain growth depends on helicity and texture, not just magnetic field.

The model links nucleation probabilities to light helicity and domain orientation.

Abstract

Controlling magnetic textures at ever smaller length and time scales is of key fundamental and technological interest. Achieving nanoscale control often relies on finding an external stimulus that is able to act on that small length scales, which is highly challenging. A promising alternative is to achieve nanoscale control using the inhomogeneity of the magnetic texture itself. Using a multilayered ferromagnetic Pt/Co/Pt thin-film structure as a model system, we employ a magnetic force microscope to investigate the change in magnetic nanotextures induced by circularly polarized picosecond laser pulses. Starting from a saturated magnetic state, we find stochastic nucleation of complex nanotextured domain networks. In particular, the growth of these domains depends not only on their macroscopic magnetization but also on the complexity of the domain texture. This helicity and texture-dependent effect contrasts with the typical homogeneous growth of magnetic domains initiated by an effective magnetic field of a circularly polarized laser pulse. We corroborate our findings with a stochastic model for the nucleation of magnetic domains, in which the nucleation and annihilation probability not only depends on the helicity of light but also on the relative magnetization orientation of neighboring domains. Our results establish a new approach to investigate ultrafast nanoscale magnetism and photo-excitation across first-order phase transitions.