Hot spin spots in the laser-induced demagnetization

TL;DR

This paper introduces the optical spin generator concept, combining optical dipole interaction and spin expectation change, to explain laser-induced femtomagnetism and identify hot spin spots in ferromagnetic nickel.

Contribution

It presents a novel framework integrating two key contributions to femtomagnetism and demonstrates its effectiveness through first-principles calculations.

Findings

Larger optical spin generator correlates with greater spin moment change.

Hot spin spots are directly linked to the optical spin generator.

The approach connects spin dynamics to electronic structure and magnetic properties.

Abstract

Laser-induced femtosecond magnetism or femtomagnetism simultaneously relies on two distinctive contributions: (a) the optical dipole interaction (ODI) between a laser field and a magnetic system and (b) the spin expectation value change (SEC) between two transition states. Surprisingly, up to now, no study has taken both contributions into account simultaneously. Here we do so by introducing a new concept of the optical spin generator, a product of SEC and ODI between transition states. In ferromagnetic nickel, our first-principles calculation demonstrates that the larger the value of optical spin generator is, the larger the dynamic spin moment change is. This simple generator directly links the time-dependent spin moment change {\Delta}Mk z (t) at every crystal- momentum k point to its intrinsic electronic structure and magnetic properties. Those hot spin spots are a direct manifestation of the optical spin generator, and should be the focus of future research.