Pulsed Heat Assisted Magnetic Recording (HAMR) is being developed to improve HAMR reliability. In conventional
HAMR systems the laser is on and at a fixed power during the writing of the entire sector. In a pulsed HAMR
implementation, the laser is turned on and off during the bit cell. For example, for a 50% duty cycle, the laser is on for
half the bit cell and off for the remainder of the bit cell. Unlike traditional HAMR where the transitions are formed
when the magnetic writer switches, in a pulsed implementation the transitions are formed during the pulsing of the laser.
In this paper we show spin stand and drive recording performance of pulsed HAMR systems and compare the outcome
to conventional recording. In particular, we show the importance and sensitivity of having proper alignment between the
phase of the optical and magnetic signals and their effect on bit error rate (BER).
KEYWORDS: Magnetism, Head, Near field scanning optical microscopy, Anisotropy, Integrated optics, Near field optics, Waveguides, Cladding, Scanning electron microscopy, Iron
Scaling the areal density, while maintaining a proper balance between media signal-to-noise,
thermal stability and writability will soon require an alternative recording technology. Heat
Assisted Magnetic Recording (HAMR) can achieve this balance by allowing high anisotropy
media to be written by heating the media during the writing process (e.g. by laser light) to
temporarily lower the anisotropy. Three major challenges of designing a HAMR head that tightly
focuses light and collocates it with the magnetic field are discussed: 1) Magnetic Field Delivery,
2)Optical Delivery, and 3) Integration of Magnetic & Optical Field Delivery Components.
Thousands of these HAMR heads were built into sliders and HGAs, and optical and scanning
electron micrograph images are shown. Scanning near-field optical microscopy (SNOM)
characterization of the HAMR head shows that the predicted ~λ/4 full-width half-maximum
(FWHM) spot size can be achieved using 488 nm light (124 nm was achieved). SNOM images
also show that wafer level fabricated apertures were able to effectively eliminate sidelobes from
the focused spot intensity profile. An MFM image of HAMR media shows that Non-HAMR
(laser power off) was not able to write transitions in the HAMR specific media even at very high
write currents, but transitions could be written using HAMR (laser power on), even at lower write
currents. A cross-track profile is shown for a fully integrated HAMR head where the magnetic
pole physical width is ~350 nm, but the written track is ~200nm, which demonstrates HAMR. A
HAMR optimization contour shows that there is an optimum write current and laser power and
that simply going to the highest write current and laser power does not lead to the best recording.
Lastly, some prospects for advancing HAMR are given and a few key problems to be solved are
mentioned.
Heat-assisted magnetic recording (HAMR), also known as hybrid recording, is one of the technologies proposed for extending hard disk drive areal densities beyond a Tb/in2. Due to their planar nature and compatibility with existing hard disk drive head fabrication techniques, dielectric optical waveguides have been suggested as a means for delivering light directly to the recording medium or near field optical transducer. In this paper we present spin stand experimental results from a dielectric optical slab waveguide fabricated on an AlTiC slider.
An experimental test bed for investigating the hybrid recording process and that allows for the precise visual alignment of the optical spot and magnetic head is described. Using this spin stand experiments have been performed on three types of hybrid recording where the critical bit dimensions are determined by using either, or both, the thermal and magnetic field profiles. By changing the relative alignment of the optical spot and magnetic head in the down track position four distinct types of marks unique to the hybrid recording process are observed.
This paper describes a design for a near field hybrid recording system that uses a mode index waveguide lens in place of a SIL or optical fiber. The mode index waveguide lens is fabricated on the back of an air bearing slider with a thin film magnetic head and giant magneto resistance (GMR) sensor for reading and writing. The optical spot from the waveguide heats the media to its Curie temperature such that within the spot a region with a reduced coercive field (`Curie cylinder') is created. The thin film head then applies a magnetic field to switch the magnetization within the Curie cylinder thereby recording a written mark. In the system proposed here, the track width of the optical spot is less than that of the thin film head and as such defines the recording track width. A GMR sensor is used to sense the flux leakage from the surface of the media and may also be laser assisted. Calculations predict an aerial density of 70 Gbits/inch2 when using a simple mode index lens fabricated from a SiO2/SiNx/SiO2 waveguide. Furthermore, by using advanced lens designs and innovative materials, the track width can be reduced further thereby offering a promising way to achieve 500 Gb/inch2.
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