Thermal stability and recording properties of sub-100 nm patterned CoCrPt perpendicular media

Abstract

Patterned magnetic media, where the bit cells are predefined, offer a potential path to ultrahigh density data storage. Here we report results on the magnetic and recording properties of islands with lateral dimensions on the order of 80 nm. Prototype nanometer-scale magnetic structures were made by patterning single-layer Co70Cr18Pt12 perpendicular media using a focused ion beam of Ga+. The effects of patterning were investigated by comparing patterned and unpatterned regions of the same medium. The magnetic reversal properties of the patterned media were obtained from magnetic force microscopy images, while those for the unpatterned media were obtained from vibrating sample magnetometer measurements. At remanence the unpatterned region decays at 1.4% per decade, whereas the patterned region shows no measurable change over the course of the experiment (5×105 s). We have also studied aspects of the recording physics of patterned media using a quasistatic write/read tester with a giant magnetoresistance head. We have written a square wave bit pattern that matches the respective island periodicity and investigated the readback signal for out-of-phase and in-phase writing.