Patterned Magnetic Recording Media – Issues and Challenges

ABSTRACTThe conventional magnetic recording approached the physical frontiers of the recording density. The magnetic recording must face the famous trilemma: In order to increase the recording density, smaller grain volumes are needed, but in order to ensure the thermal stability of recorded information, the anisotropy constant should be increased accordingly; what results is an increased anisotropy field, which requires higher writing fields. Such fields are unavailable with the maximum saturation magnetization obtainable with the magnetic materials of the current heads. In order to overcome these problems, new media structures have been proposed. The most promising is the bit-patterned magnetic media (BPM), intensively studied over the last years with the aim of obtaining obtain an ultra-high recording density of hard-disk drives. A BPM comprises monodisperse high-anisotropy nano-particles in a self-organized patterning. They have a higher thermal stability, a lower noise and a higher signal resolution, which leads to a higher recording density and a better SNR. They eliminate the transition noise and, due to the large fraction of the bit volume occupied by the magnetic dots, improve thermal stability. Nevertheless, some important issues such as long-range patterning, control of the surface roughness, signal readout, etc., remain critical problems to solve. Another challenge is the fact that recording on BPM is sensitive to the material and geometry parameter fluctuations that may lead to additional constraints and require tight synchronization of the write-field misregistration time and bit positions. A possible route to higher recording densities is to use a multilevel recording, where more than two states are stored per dot.

Towards low energy consumption data storage era using phase-change probe memory with TiN bottom electrode

Phase-change probe memory has been extensively regarded as one of the most prospective candidates to satisfy the recording density requirement from the incoming age of big data. However, in spite of recent advances, the energy consumption of phase-change probe memory still remains fairly high due to the use of the diamond-like carbon bottom electrode usually having a relatively high electric resistivity. In this case, the possibility of using titanium nitride to replace the diamond-like carbon as the electrode materials is investigated in this paper. The thickness and time-dependent resistivity of titanium nitride film is measured, allowing for a more conductive characteristic and a better stability than diamond-like carbon film at the same condition. Consequently, the writing of crystalline bit using the previously designed phase-change probe memory architecture but with titanium nitride bottom electrode is performed experimentally, and results show that using titanium nitride as bottom electrode would enable an achievement of ultra-high recording density with lower energy consumption than the phase-change stack with diamond-like carbon electrode.