Revealing the nature of the ultrafast magnetic phase transition in Ni by correlating extreme ultraviolet magneto-optic and photoemission spectroscopies

TL;DR

This study uses extreme ultraviolet spectroscopies to reveal the universal ultrafast magnetic phase transition in Ni, explaining its magnetic response across different laser fluences and identifying coexisting phases during recovery.

Contribution

It correlates two ultrafast spectroscopic techniques to uncover the universal nature and detailed dynamics of Ni's magnetic phase transition at femtosecond timescales.

Findings

Ultrafast demagnetization occurs within 20 fs.

Magnetization recovers over 500 fs to >70 ps.

Evidence of coexisting phases with distinct recovery timescales.

Abstract

By correlating time- and angle-resolved photoemission and time-resolved transverse- magneto- optical Kerr effect measurements, both at extreme ultraviolet wavelengths, we uncover the universal nature of the ultrafast photoinduced magnetic phase transition in Ni. This allows us to explain the ultrafast magnetic response of Ni at all laser fluences - from a small reduction of the magnetization at low laser fluences, to complete quenching at high laser fluences. Both probe methods exhibit the same demagnetization and recovery timescales. We further show that the ultrafast demagnetization in Ni is indeed a magnetic phase transition that is launched within 20 fs, followed by demagnetization of the material within ~200 fs, and subsequent recovery of the magnetization on timescales ranging from 500 fs to >70 ps. We also provide evidence of two competing channels with two distinct timescales in the recovery process, that suggest the presence of coexisting phases in the material.