Grazing-incidence optical magnetic recording with super-resolution.

Gunther Scheunert,Paul Dawson,Dan Oron,Ora Bitton,Ifat Kaplan-Ashiri,Katya Rechev,René Kullock,Sidney R Cohen,Bert Hecht,Ryan Mccarron

doi:10.3762/bjnano.8.4

Abstract

Heat-assisted magnetic recording (HAMR) is often considered the next major step in the storage industry: it is predicted to increase the storage capacity, the read/write speed and the data lifetime of future hard disk drives. However, despite more than a decade of development work, the reliability is still a prime concern. Featuring an inherently fragile surface-plasmon resonator as a highly localized heat source, as part of a near-field transducer (NFT), the current industry concepts still fail to deliver drives with sufficient lifetime. This study presents a method to aid conventional NFT-designs by additional grazing-incidence laser illumination, which may open an alternative route to high-durability HAMR. Magnetic switching is demonstrated on consumer-grade CoCrPt perpendicular magnetic recording media using a green and a near-infrared diode laser. Sub-500 nm magnetic features are written in the absence of a NFT in a moderate bias field of only μ0H = 0.3 T with individual laser pulses of 40 mW power and 50 ns duration with a laser spot size of 3 μm (short axis) at the sample surface – six times larger than the magnetic features. Herein, the presence of a nanoscopic object, i.e., the tip of an atomic force microscope in the focus of the laser at the sample surface, has no impact on the recorded magnetic features – thus suggesting full compatibility with NFT-HAMR.

Highlights

Heat-assisted magnetic recording (HAMR) is widely considered the most promising future candidate for achieving some major goals in magnetic storage technology [1,2]
Using an ordinary commercial hard disk drives (HDDs) platter we demonstrate, by proper choice of parameters, that even laser powers comparable to surface plasmon resonator (SPR)-HAMR already cause magnetic switching in the presence of a homogeneous magnetic bias field of μ0HB = 0.3 T – at a resolution six times smaller than the laser spot size
Details of the remnants of individual bits, which are still visible in the magnetic force microscopy (MFM) scans, are mostly not visible in the line-profiles below because of running average performed on the graphical data

Summary

Introduction

Heat-assisted magnetic recording (HAMR) is widely considered the most promising future candidate for achieving some major goals in magnetic storage technology [1,2]. The magnetic field is switched off and the bit is “frozen” in its new magnetic state. This process is akin to the magnetization of macroscopic permanent magnets, which are heated above their Curie point in a homogeneous magnetic bias field during fabrication to assure the highest possible energy product. At the heart of HAMR devices is a near-field transducer (NFT): a device which consists of a light-capturing unit like a coupling grating, a waveguide structure and a surface plasmon resonator (SPR) positioned in immediate proximity to the recording media to generate a strong near field for highlylocalized inductive heating of the recording layer during the writing process [6,7]

Results

Discussion

Conclusion