Magnetic spin moment reduction in photoexcited ferromagnets through exchange interaction quenching: Beyond the rigid band approximation

Abstract

The exchange interaction among electrons is one of the most fundamental quantum mechanical interactions in nature and underlies any magnetic phenomena from ferromagnetic ordering to magnetic storage. The current technology is built upon a thermal or magnetic field, but a frontier is emerging to directly control magnetism using ultrashort laser pulses. However, little is known about the fate of the exchange interaction. Here we report unambiguously that photoexcitation is capable of quenching the exchange interaction in all three $3d$ ferromagnetic metals. The entire process starts with a small number of photoexcited electrons which build up a new and self-destructive potential that collapses the system into a new state with a reduced exchange splitting. The spin moment reduction follows a Bloch-like law as $M_z(\Delta E)=M_z(0)(1-\Delta E/\Delta E_0{)}^{\frac{1}{\beta }}$, where $\Delta E$ is the absorbed photon energy and $\beta$ is a scaling exponent. A good agreement is found between the experimental and our theoretical results. Our findings may have a broader implication for dynamic electron correlation effects in laser-excited iron-based superconductors, iron borate, rare-earth orthoferrites, hematites and rare-earth transition metal alloys.

16 pages, 3 figures, one supplementary material file

References in corpus (4)

• Super-Diffusive Spin-Transport as a Mechanism of Ultrafast Demagnetization
• Tracking Cooper Pairs in a Cuprate Superconductor by Ultrafast Angle-Resolved Photoemission
• Abrupt transition in quasiparticle dynamics at optimal doping in a cuprate superconductor system
• Ultrafast dynamics and fragmentation of C60 in intense laser pulses

Cited by in corpus (1)

• All-optical spin switching: A new frontier in femtomagnetism -- A short review and a simple theory