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Last Updated on Oct.20, 2010 Welcome to Group M04 at State Key Laboratory, IPCAS!

Introduction 

 

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. By virtue of their extremely small size, nanomagnets possess significantly different properties from their parent bulk materials. The 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.

2. Research plan and expected outcome

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The central strategy of this project is to artificially control the growth of nanostructure on supporting substrate with atomic precision and investigate the magnetism as well as ultrafast demagnetization in low dimensional confined magnetic system. The 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 magnetic nanostructures

 By means of molecular beam epitaxy (MBE), artificially design and grow magnetic nanostructures, such as, magnetic quantum dots, nanowires and ultrafilms on supporting substrate with atomic precision;

By 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 magnetization measurements.

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 technique to investigate the coupling  and magnetic properties of nanodots without any approximation.

   (d) Ultrafast spin dynamics and Femtomagnetism

By 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.

Understand  the 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.



State Key Laboratory of Magnetism, Institute of Physics, CAS
P.O. Box 603, Bejing 100080, P. R, China
Tel: 086-10-82648083 Fax: 086-10-82649485
E-mail:  zhcheng@aphy.iphy.ac.cn

Copyright © 2005 Group M04, State Key Lab. of Magnetism, IOP, CAS