Magnetisation reversal and thermal activation in CoCrPt patterned media

Abstract

Co70Cr18Pt12 perpendicular media has been patterned using a focussed beam of Ga+ ions (FIB) into arrays of sub -100nm islands suitable for demonstrating high density recording. The islands show single domain behaviour below a critical size, which in this case is approximately 110nm. In order to characterise the change to the magnetic properties introduced by FIB patterning, we have measured reversal properties including switching field distributions and thermal decay rates by magnetic force microscopy (MFM) imaging and Kerr rotation. The MFM was used to measure small arrays of islands by counting reversed islands at remanence as a function of reverse field or decay time. The Kerr measurements were averaged over larger arrays using a ∼20um focussed laser beam. As a comparison unpatterned media was measured both using Kerr rotation and vibrating sample magnetometer (VSM).