Ultimate limits to thermally assisted magnetic recording

TLDR

Thermally assisted magnetic recording uses heat to write on high‑anisotropy media, promising higher storage densities but raising questions about writability, long‑term stability, heating above the Curie point, cooling rates, and system architecture. The study aims to evaluate how temperature‑dependent magnetization and anisotropy affect stability, devise localized heating methods, integrate patterned media to reach ultimate density limits, and enable reliable readout of the smallest bits. The authors analyze the temperature dependence of magnetization and anisotropy using the stability metric MV Hk.

Abstract

The application of thermal energy to enable recording on extremely high anisotropy magnetic media appears to be a viable means of extending the density of stored information. The central physical issue facing the technology is what gain can be realized in writability along with long-term data stability using imaginable media materials. We reasonably expect the material properties M(T) and Hk(T) to determine this, since a stability metric for media with characteristic magnetization switching unit volume V is MV Hk/2kBT. This matter is controversial owing to still open questions related to thermomagnetic recording with temperature elevation above the Curie point and optimal cooling rates. There are indications that multi-component magnetic media may offer advantages in achieving performance goals. Beyond the physical issues lie engineering matters related to the correct system architecture to yield a practical storage device to meet future customer expectations. Here one must address a detailed means of delivering localized heating to the magnetic medium to perform efficient recording. To date, magnetic recording devices have been highly mechanical systems, so it is natural to inquire how a need for an aggressively heated head–medium interface could impact the evolution of future systems. Eventually elements of thermally assisted recording could be combined with patterned media approaches such as self-organized magnetic arrays to push toward ultimate limits where the thermal instability of bits overtakes engineered media materials. Finally, a practical recording system cannot be realized unless a means of finding, following, and reading the smallest bits with a usable signal-to-noise ratio exists—engineering issues separate from an ability to reliably record those bits.