Details of Grant 

EPSRC Reference:	GR/T20151/01
Title:	High Field and Picosecond Magnetisation Reversal Spectroscopy of AFC and Perpendicular Media
Principal Investigator:	Wu, Dr J
Other Investigators:
Researcher Co-Investigators:
Project Partners:
Department:	Physics
Organisation:	University of York
Scheme:	First Grant Scheme Pre-FEC
Starts:	01 January 2005	Ends:	31 January 2007	Value (£):	121,479
EPSRC Research Topic Classifications:	Materials Characterisation
EPSRC Industrial Sector Classifications:	Electronics
Related Grants:
Panel History:
Summary on Grant Application Form
With the increasing demand for high density and speed in information storage, the behaviour of magnetisation on small dimension and short time scales has become one of the most important issues in fundamental and industrial magnetism. The basic operation of Giant Magneto-Resistance (GMR) spin valves and Magnetic Random Access Memory (MRAM) is the fast reversal of magnetic thin film elements in magnetic field pulses. As the data rate approaching GHz range and the data density exceeding 150 Mbit/mm2 (100 Gbit/in2), dynamic magnetisation mapping at nanometer-length scale and sub-nanosecond temporal resolutions are demanded for material analysis and device characterisation, which are beyond the limits of traditional imaging techniques. Time-resolved scanning Kerr microscopy has recently emerged and demonstrated its power in imaging fast dynamics of sample magnetisation directly (not the strain field around it) at femto and picosecond temporal resolution. However so far the studies are limited to soft material structures because in the present technique the coplanar transmission line structures used to launch the current pulses cannot withstand high voltage pulses and can only provide pulsed magnetic fields less than 1 kOe (1Oe=80A/m). Hard magnetic materials, which are suitable for recording media, have a typical coercivity of a few kOe. The micro/nano scale magnetic dots and wires, an important nanomaterial system with the applications in patterned media, spintronics, quantum computing, and bio-sensors, also shown an increased coercivity up to a couple of kOe with decreasing thicknesses and sizes. So larger magnetic field pulses are needed in order to drive the sample magnetisation and investigate reversal dynamics in these advanced magnetic structures.In this project, I will employ a unique technique to produce high and uniform transient magnetic field pulses with amplitude of up to 10 kOe at picosecond rise time by using a novel microstrip line structure with an optical window to launch the current pulses. This microstrip line structure will have a breakdown voltage much higher than that of a coplanar transmission line structure, and hence produce high magnetic fields. The optical window will be fabricated from a transparent and conductive Indium Tin Oxide (ITO) film and integrated into the top conductor of the microstrip line structure. Combined with Kerr spectroscopy, I will set up a world-first high-field high-frequency time-resolved Kerr spectroscope, which will be a large step beyond the state of the art. Using this new set-up, I will investigate picosecond time-domain phenomena in antiferromagnetic coupled (AFC) multilayer structures and magnetic thin films with perpendicular anisotropy, which has rarely been explored due to the limit of the pulsed field strength of the current techniques. The AFC multilayer structures have recently attracted a lot of interests due to its potential in extending a real density in magnetic recording media beyond the predicted superparamagnetic limit. The effects of interlayer exchange coupling and intergranular exchange coupling on the magnetisation fast reversal in AFC structures is still an open issue. The thin films with perpendicular anisotropy have the potential of ultrahigh density recording and better thermal stability, and the factors controlling the fast reversal such as film structure, demagnetising field, thickness of the soft underlayer are waiting for experimental investigations. This project will explore the fundamental physics in picosecond time-domain of spin dynamic reversal in antiferromagnetic coupled sandwich structures and thin films with perpendicular anisotropy, and the knowledge to be obtained is also believed to be crucially important to information technology.
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Organisation Website:	http://www.york.ac.uk