Seminar 22nd July 2010 11:30 a.m. University of Southampton, Physics Seminar Room (5th floor, Building 46)
Exchange Spring Magnetic Thin Films: The Future Recording Media?
Dr Chris Morrison
University of Manchester's Nano Engineering and Storage Technologies Research Group (NEST)
- Web page
- http://nest.cs.manchester.ac.uk/people/
- Categories
- Materials, Micromagnetics, Spintronics
- Submitter
- Petrina Butler
University of Manchester's Nano Engineering and Storage Technologies Research Group (NEST)
Chris worked within Southampton's Magnetism and Superconductivity group from 2005 to 2009 where he completed his doctoral thesis on the exchange-spring magnetic media, and this talk will not only provide a broad overview of magnetic recording in general, but also provide an excellent opportunity to see how Chris has developed and extended his work on novel exchange-spring systems.
Abstract
Granular CoCrPt-oxide magnetic recording media have been used in all perpendicular hard disk drives since their inception in the middle of the last decade. Exchange spring or exchange coupled composite (ECC) recording media have been proposed as a route for extending hard disk drive areal density to 1Tbit/in2 and beyond. These media rely on an incoherency of reversal between two magnetically dissimilar phases, producing an enhanced torque-driven reversal while maintaining a high perpendicular anisotropy. As such, ECC media provide stability against thermally-driven magnetic reversal while keeping switching fields within acceptable levels for recording purposes. Granular CoCrPt-oxide films with a lower anisotropy, CoCrPt-based cap are characterised magnetically in order to determine the extent to which their switching behaviour is modified from the single phase granular material. Angular remanence measurements performed using a state-of-the-art vector vibrating sample magnetometer reveal a distinct modification of the switching behaviour of these CoCrPt-oxide ECC media with the presence/absence of an exchange control layer and variation in cap thickness. Addition of a thin exchange control layer between the magnetic layers allows the degree of exchange interaction and the coherency of rotation between the two layers to be tuned. The angle dependence of remanence allows the reversal mechanisms of magnetic media to be explored and, in particular, comparison of experimental data with models of switching mechanisms (Stoner-Wohlfarth coherent reversal and Kondorsky domain wall motion) allows coupling to be characterised. We demonstrate that exchange coupling in these systems and consequently switching behaviour can be successfully tailored, providing both insight into the origin of inter-layer and inter-granular coupling and the prospect of optimising their magnetic properties for recording applications.
Organised by Dr. A. Roger Buckingham
School of Physics and Astronomy / Optoelectronics Research Centre
University of Southampton
t: +44 (0)23 8059 2104 / +44 (0)23 8059 3143