Alexander S. Chernyshov

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.

Thermal Layers Effect on Recording Performance in HAMR

Recording experiments were performed on FePt media with varying thermal layers thickness values. As the heat sink increases we observe that jitter decreases, due to improved thermal gradient. At the same time the laser power required to write on media increases. A semianalytical integrated optical and thermal model sheds light onto these experimental findings.