Ultrafast selective mid-infrared sublattice manipulation in the ferrimagnet $FeCr_2S_4$

TL;DR

This study demonstrates ultrafast, selective control of magnetic sublattices in FeCr2S4 using resonant mid-infrared laser pulses, revealing distinct dynamics of Fe and Cr sublattices through time-resolved magneto-optic Kerr effect measurements.

Contribution

It introduces a method for selective, ultrafast manipulation of magnetic sublattices via resonant mid-infrared excitation in ferrimagnetic materials.

Findings

Resonant mid-infrared pulses selectively excite Fe sublattice.

Fe sublattice exhibits slower magnetic dynamics under resonant excitation.

Off-resonant pumping affects both Fe and Cr sublattices simultaneously.

Abstract

$FeCr_2S_4$ is a ferrimagnet with two oppositely ordered spin sublattices (Fe and Cr), connected via superexchange interaction, giving a non-zero net magnetic moment. We show, using time-resolved measurements of the magneto-optic Kerr effect, how the magnetic dynamics of the sublattices can be selectively manipulated by resonantly perturbing the Fe sublattice with ultrashort laser pulses. The mid-infrared excitation through intra-atomic Fe $d$-$d$ transitions triggers markedly slower dynamics in comparison to an off-resonant pumping affecting both of the two sublattices simultaneously. By changing probe wavelength to move in and out of resonance with the Fe $d$-$d$ transitions, we also show the specific contributions of the Fe sublattice to these dynamics.