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NanoMat 2018 Nano Research & Applications
ISSN: 2471-9838 Page 80
April 26-27, 2018
Rome, Italy
17th Edition of International Conference on
Emerging Trends in
Materials Science and
Nanotechnology
Ultrafast processes involving the electrons and spins are
important issues for both fundamental science and for the
potential applications in spintronics. Application of ultrashort
infra-red laser pulses allows ultimately the manipulation of the
local magnetization in magnetic films. In order to understand the
changeoftheinitialmagneticorstructuralstate,inducedbyIRlaser
pulses, it is essential to describe the individual and fundamental
processes taking place during the first hundred femtoseconds.
Since the first observation of laser induced spin dynamics, the
mechanisms responsible for the femtosecond demagnetization
have been widely debated, but no consensus could be found until
today. Time-resolved x-ray magnetic circular dichroism (XMCD)
using synchrotron facilities and x-ray free electron sources have
provided femtosecond time resolution and thus new information
concerning femtosecond demagnetization dynamics. XMCD
spectroscopy is an element-specific tool which can be used to
study ultrafast magnetization, with chemical resolution. At soft
x-ray energies it is now possible to measure the dynamics of the
spin and orbital magnetic moments with temporal resolution of
~100 fs. Recent results using the potential of the XMCD technic,
show that right after the IR laser excitation, interatomic transfer of
angular moment takes place at the femtosecond scale, whereas
the global demagnetization proceeds, illustrating one of the most
efficient way of conservation of angular moment, during the loss
of magnetization in the system. In recent works, it was shown
that laser induced electron current activates sizable ultrafast
dynamics too. Different theoretical approaches propose different
microscopic models which are nowadays strongly debated.
Our recent results show that such hot-electron current induced
ultrafast dynamics produces two different characteristic times of
demagnetization in rare earth 4f as well as in transition metal 3d
elements in 4f-3d alloys. The results can be related to propagation
times and velocities of the hot-electron pulses.
Ultrafast demagnetization dynamics by time resolved XMCD
Christine Boeglin
IPCMS, CNRS - University of Strasbourg, France
Nano Res Appl, Volume:4
DOI: 10.21767/2471-9838-C1-009