Nanomagnetism and Femotomagnetism
1. Scientific significance of research
The objectives of modern data storage industry can be summarized by
the slogan ˇ°smaller and faster.ˇ±
The rapid development in fabrication and
applications of nanostructured magnetic devices drives us to
understand the magnetism of low-dimensional system.
virtue of their extremely small size, nanomagnets possess
significantly different properties from their parent bulk materials.
demands for the ever-increasing speed of storage of information in
magnetic media plus the intrinsic limitations that are connected
with the generation of magnetic field pulses by current have
triggered intense searches for ways to control magnetization by
means other than magnetic fields.
Manipulating and controlling magnetization with ultrashort laser
pulses has become an alternative approach.
Femtosecond laser pulses offer the intriguing possibility to probe a
magnetic system on a time scale that
corresponds to the (equilibrium) exchange interaction, responsible
for the existence of magnetic order, while being much faster than
the time scale of spin-orbit interaction(1¨C10 ps) or magnetic
precession (100¨C1000 ps). Despite being the subject of intense
research for over a decade, the underlying mechanisms that govern
the demagnetization remain unclear. The corresponding mechanism has
its origin in relativistic quantum electrodynamics, beyond the
spin¨Corbit interaction involving the ionic potential. Laser-induced
femtosecond magnetism or femtomagnetism opens a new frontier for a
faster magnetic storage device, but probing such a fast
magnetization change is a big challenge.
plan and expected outcome
central strategy of this project is to artificially
control the growth of nanostructure on supporting substrate with
precision and investigate the magnetism as well as ultrafast
in low dimensional confined magnetic system.
rich physics associated with these magnetic nanostructures provides
ample testament that nanophase magnetic materials are not just
smaller but also different! We have developed a powerful combination
of methods, which allow us not only to grow two dimensional (2D)
ultrathin films, one-dimensional stripes, and zero dimensional dots,
but also to investigate the structure, magnetic structure, magnetic
properties and ultrafast spin dynamics.
(a) Artificially design and controllable growth of
molecular beam epitaxy
design and grow magnetic nanostructures, such as, magnetic quantum
dots, nanowires and ultrafilms on supporting substrate with
using bottom-up approach,
synthesis monodisperse magnetic nanoparticle self-assembly from
molecular-precursor building blocks.
(b) Spin-orbit coupling and manipulation of magnetic anisotropy
in Low Dimensional Confined Magnetic System
Investigate the effect of dimensionality on the magnetic properties
and the enhancement of magnetic moments and magnetic anisotropy in
small magnetic nanoclusters by means of in-situ SMOKE, together with
Manipulate magnetic anisotropy via by modifying the step density of
substrates, obliquely incident deposition and stress between
substrate and film.
(c) Tailoring the ferromagnetic coupling of magnetic nanodots
Tune the ferromagnetic coupling of magnetic nanodotsvia
dimensionality variation of of the Mediating Electrons by changing
metallic, semiconducting or insulating substrates.
By integrating the
fast Fourier transform (FFT) method into
the Monte Carlo simulation by means of cluster multiple labeling
to investigate the coupling and magnetic
properties of nanodots without any approximation.
(d) Ultrafast spin dynamics and Femtomagnetism
using a scanning Kerr microscope with a temporal resolution of 100
fs and a spatial resolution of 500 nm, to investigate the ultrafast
demagnetization and recovery processes of magnetic nanostructure.
roles of spin-orbit, spin-lattice, and electron-lattice interactions
in the ultrafast optical control of magnetism
Explore the new approach for manipulating
and controlling magnetization with ultrashort laser pulses.