Selection rules for all-optical magnetic recording in iron garnet

A Stupakiewicz,A K Zvezdin,M D Davydova,A Kirilyuk,A V Kimel,K Szerenos,K A Zvezdin

doi:10.1038/s41467-019-08458-w

Abstract

Rapid growth of the area of ultrafast magnetism has allowed to achieve a substantial progress in all-optical magnetic recording with femtosecond laser pulses and triggered intense discussions about microscopic mechanisms responsible for this phenomenon. The typically used metallic medium nevertheless considerably limits the applications because of the unavoidable heat dissipation. In contrast, the recently demonstrated photo-magnetic recording in transparent dielectric garnet for all practical purposes is dissipation-free. This discovery raised question about selection rules, i.e. the optimal wavelength and the polarization of light, for such a recording. Here we report the computationally and experimentally identified workspace of parameters allowing photo-magnetic recording in Co-doped iron garnet using femtosecond laser pulses. The revealed selection rules indicate that the excitations responsible for the coupling of light to spins are d-d electron transitions in octahedral and tetrahedral Co-sublattices, respectively.

Highlights

Rapid growth of the area of ultrafast magnetism has allowed to achieve a substantial progress in all-optical magnetic recording with femtosecond laser pulses and triggered intense discussions about microscopic mechanisms responsible for this phenomenon
It has been shown that using a single 50 fs laser pulse one can permanently switch the magnetization in Codoped yttrium iron garnet thin film (YIG:Co) with (001) plane of the sample10
Aiming to define the workspace of the key parameters allowing the switching, we developed a phenomenological model of the photo-induced magnetization dynamics in YIG:Co film based on the Landau–Lifshitz–Gilbert (LLG) equation:

Summary

Introduction

Rapid growth of the area of ultrafast magnetism has allowed to achieve a substantial progress in all-optical magnetic recording with femtosecond laser pulses and triggered intense discussions about microscopic mechanisms responsible for this phenomenon. Speaking in general finding an electronic transition a subtle excitation of which can launch dramatic changes of electric, optical or magnetic properties of media is one of the long-standing dreams in the field of photo-induced phase transitions1–5 This field got a great boost due to the development of new femtosecond laser sources allowing to explore photo-induced phase transitions in a broad spectral range and on a time scale of elementary processes in condensed matter such as electron–electron, electron–lattice, spin–lattice interactions, period of oscillations of lattice atoms, or spins. It has been shown that using a single 50 fs laser pulse one can permanently switch the magnetization in Codoped yttrium iron garnet thin film (YIG:Co) with (001) plane of the sample10 In this material, the Co-dopants are responsible for strong magnetocrystalline anisotropy, making cube diagonals to be eight easy directions. We reveal these transitions and open up the way for theoretical and computational studies of all-optical magnetic recording and ultrafast photo-magnetic phase transitions in dielectrics

Methods

Results

Conclusion