Controlling the Polarity of the Transient Ferromagnetic-Like State in Ferrimagnets

TL;DR

This paper demonstrates how the polarity of a transient ferromagnetic-like state in ferrimagnets can be controlled by initial temperature, using atomistic simulations and micromagnetic theory, advancing ultrafast magnetic device applications.

Contribution

It reveals the temperature-dependent control mechanism of the transient ferromagnetic-like state in ferrimagnets through detailed modeling.

Findings

The response speed of lattice magnetic moments depends on temperature.

Low temperatures favor transition metal response; high temperatures favor rare earth response.

Temperature control can manipulate the polarity of the transient ferromagnetic state.

Abstract

After the application of an ultrashort laser pulse, the antiferromagnetic alignment in rare earth-transition metal alloys can temporarily become ferromagnetic with the rare-earth polarity. Proposed models merely describe this effect, without showing the route for its manipulation. Here we use extensive atomistic spin model simulations and micromagnetic theory for ferrimagnets at elevated temperatures to predict that the polarity of this transient ferromagnetic-like state can be controlled by initial temperature. We show that this arises because the magnetic response of each lattice has a different temperature dependence, at low temperatures the transition metal responds faster than the rare earth, while at high temperatures this role is interchanged. Our findings contribute to the physical understanding and control of this state and thus open new perspectives for its use in ultrafast magnetic devices.