Hot electron driven enhancement of spin-lattice coupling in 4f ferromagnets observed by femtosecond x-ray magnetic circular dichroism

TL;DR

This study uses femtosecond x-ray magnetic circular dichroism to observe ultrafast demagnetization in Gd and Tb, revealing that excited state spin-lattice coupling is significantly enhanced compared to equilibrium.

Contribution

It demonstrates the enhancement of spin-lattice coupling in 4f ferromagnets during electronic excitation using femtosecond x-ray techniques.

Findings

Ultrafast demagnetization time of 750 fs in Gd and Tb.

Slower demagnetization times of 40 ps in Gd and 8 ps in Tb.

Spin-lattice coupling is enhanced by orders of magnitude in excited states.

Abstract

Femtosecond x-ray magnetic circular dichroism was used to study the time-dependent magnetic moment of 4 fs electrons in the ferromagnets Gd and Tb, which are known for their different spin-lattice coupling. We observe a two-step demagnetization with an ultrafast demagnetization time of 750 fs identical for both systems and slower times which differ sizeably with 40 ps for Gd and 8 ps for Tb. We conclude that spin-lattice coupling in the electronically excited state is enhanced up to orders of magnitude compared to equilibrium.