David Treves

Design of a manufacturable discrete track recording medium

The potential benefits of patterning discrete tracks onto a disk for magnetic data storage have long been investigated. A practical process for manufacturing a cost-effective discrete track recording (DTR) medium has prevented such a disk from being introduced into a product. In this paper, a process utilizing nano-imprint lithography techniques to create a land and groove structure on the surface of a disk substrate will be described. Design considerations for the geometry of the structure, as well as of the magnetic write and read widths of the head, are discussed. Data showing the magnetic characteristics and recording performance of a DTR medium are also presented.

Measurement of Magnetic Properties Relevant to Heat-Assisted-Magnetic-Recording

Heat-assisted magnetic recording (HAMR) is likely the successor of perpendicular magnetic recording (PMR) technology. The quality of HAMR writing is dominated not by the magnetic field gradient (as in PMR), but by the high thermal gradient generated by the laser heating spot. Knowledge of temperature dependence of magnetic parameters: anisotropy field Hk(T), saturation moment Ms(T) and anisotropy field distribution (δHk) the proximity of Curie temperature is crucial for media development. Here we describe a new system to probe the magnetic properties close to Tc, as well as a semianalytical model to explain the results. The model takes into account the thermal fluctuations; input into the model are experimentally measured data for Ms(T), Hk(T), mean field demagnetization factor, σHk and grain size distribution. In the paper we present two types of data: 1) thermal erasure in the absence of a magnetic field; and 2) thermomagnetic writing, allowing the estimate of the switching field distribution at high temperatures.