Ultrafast photo-magnetic recording in transparent medium

TL;DR

This paper demonstrates ultrafast, low-heat, all-optical magnetic recording in transparent ferrimagnetic garnet films using femtosecond laser pulses, enabling deterministic control of magnetic states at room temperature.

Contribution

It introduces a novel mechanism for magnetic switching in transparent dielectrics with femtosecond laser pulses, avoiding heat-related limitations of previous methods.

Findings

Magnetic switching occurs within 20 ps.

Low heat load of less than 6 J/cm3.

Deterministic control of magnetic bits using laser polarization.

Abstract

Finding a conceptually new way to control the magnetic state of media with the lowest possible production of heat and simultaneously at the fastest possible time-scale is a new challenge in fundamental magnetism [1-4] as well as an increasingly important issue in modern information technology [5]. Recent results demonstrate that exclusively in metals it is possible to switch magnetization between metastable states by femtosecond circularly polarized laser pulses [6-8]. However, despite the record breaking speed of the switching, the mechanisms in these materials are directly related to strong optical absorption and laser-induced heating close to the Curie temperature [9-12]. Here we report about ultrafast all-optical photo-magnetic recording in transparent dielectrics. In ferrimagnetic garnet film a single linearly polarized femtosecond laser pulse breaks the degeneracy between metastable magnetic states and promotes switching of spins between them. Changing the polarization of the laser pulse we deterministically steer the net magnetization in the garnet, write "0" and "1" magnetic bits at will. This mechanism operates at room temperature and allows ever fastest write-read magnetic recording event (< 20 ps) accompanied by unprecedentedly low heat load (< 6 J/cm3).