SUB-PICOSECOND CONTROL OF NANO-MAGNETS

Lead Research Organisation: University of Exeter
Department Name: Physics

Abstract

The data storage capacity and the speed of operation of a modern laptop computer are orders of magnitude greater than those of the first computers that occupied several large rooms. To maintain the pace of progress, both the physical bit size and the data access time must be reduced even further. Under these circumstances, the nano-magnetic technology is becoming one of the strongest players in the multibillion dollar market for high speed miniature devices for data storage and processing.This constitutes the main practical motivation for the proposed research programme which has the overall aim of gaining an ever-faster control of nanoscale magnetic structures by means of sub-picosecond optical and magnetic pulses. This will require that several issues of fundamental importance be resolved, extending our knowledge and understanding of ultrafast nano-scale magnetic dynamics to a new level.The basic phenomenon exploited in the project is the Inverse Faraday Effect due to which circularly polarised optical pulses can generate sub-picosecond pulses of magnetic field (so called photo-magnetic field), which are orders of magnitude shorter than the fastest electrical and magnetic pulses produced electronically or in ultrafast photo-diodes. The pulsed photo-magnetic field due to optical pulses from an ultrafast laser will be used to manipulate the magnetisation either directly, by using the photo-magnetic field itself, or indirectly, by converting it into pulses of the Oersted magnetic field within a novel device called a Faraday Optical Transformer. The magnetisation precession excited in magnetic thin films and nanoscale elements will be then traced magneto-optically by measuring the change of polarisation acquired by a delayed optical pulse (a probe ) upon reflection from the pumped sample. The magnetisation dynamics will be studied and imaged in both small (spin waves) and large (180 degrees reversal) amplitude regimes. A combined action of multiple pulses of photo-magnetic, Oersted and / or microwave fields will be investigated and used to optimize magnetic switching characteristics.The proposed research falls within the EPSRC's Nano World (Magnetic materials), Quantum Realm (Interaction of Light and Matter), and Miniature Machines (Photonics and Optoelectronics) priority areas.
 
Description Definition of the research field of magnonics as the study of spin waves (waves of magnetisation, the quanta of which are called "magnons") and technology of spin wave ("magnonic") devices and metamaterials.

Control of the dispersion of collective spin wave modes in arrays of magnetic nanoelements by tailoring the geometry of the constituent nanoelements.

Resonant coupling of free space microwaves into spin waves with orders of magnitude shorter wavelength.

Magnetically programmable magnonic valve and phase shifter.

Time resolved optically pumped scanning optical microscopy (TROPSOM) and its application to imaging of spin waves excited in thin magnetic films, magnonic crystals and metamaterials by focused femtosecond laser pulses.

Curvature induced anisotropy in curved magnonic waveguides.
Exploitation Route Continuing the research with an eventual application within consumer products.
Sectors Electronics,Energy
 
Description Further investigations in the relevant research fields.
First Year Of Impact 2009