# Ultrafast optically induced ferromagnetic/anti-ferromagnetic phase transition in GdTiO$_3$ from first principles

## TL;DR

This study demonstrates that intense mid-infrared light can dynamically induce a magnetic phase transition in GdTiO3 from ferromagnetic to antiferromagnetic using first-principles calculations, revealing a new method for controlling magnetic states.

## Contribution

The paper introduces a novel approach to control magnetic phases dynamically via nonlinear phonon coupling, specifically in GdTiO3, expanding the possibilities beyond static strain and chemical methods.

## Key findings

- Mid-infrared excitation induces a ferromagnetic to antiferromagnetic transition.
- Jahn-Teller distortion and Gd displacement are key to the phase change.
- Octahedral rotations have minimal impact on the transition.

## Abstract

Epitaxial strain and chemical substitution have been the workhorses of functional materials design. These static techniques have shown immense success in controlling properties in complex oxides through the tuning of subtle structural distortions. Recently, an approach based on the excitation of an infrared active phonon with intense mid-infrared light has created an opportunity for dynamical control of structure through special nonlinear coupling to Raman phonons. We use first-principles techniques to show that this approach can dynamically induce a magnetic phase transition from the ferromagnetic ground state to a hidden antiferromagnetic phase in the rare earth titanate GdTiO$_3$ for realistic experimental parameters. We show that a combination of a Jahn-Teller distortion, Gd displacement, and infrared phonon motion dominate this phase transition with little effect from the octahedral rotations, contrary to conventional wisdom.