On the other hand energy assisted magnetic recording uses heat, or a high frequency magnetic field to temporarily lower the reversal field of granular high-K U media while maintaining high stability at rest or during the reading process. In the extreme case of bit pattern media, one magnetic island corresponds to one bit, whose volume can be increased compared with the grain size in conventional media, resulting in increased thermal stability. On one hand, the patterned media approach proposes either to physically define track within current granular media (DTM) or to lithographically define magnetic islands (BPM). Therefore prospects for data areal densities above 1 Tb in −2 involve novel advanced media schemes either using a patterned media or energy assisted recording ( Fig. Most experts currently expect it to reach close to 1 Tbit in −2, which at current annual growth rates could be reached within the next 3–5 years. However, how far the areal density can ultimately be pushed with continuous granular media is an open question of great technological and economical consequences.
Significant work is also carried out on new multilayer concepts like exchange coupled continuous (ECC). Looking for materials or methods to obtain high magnetic anisotropy in recording media could help to improve thermal stability.
Finding more suitable materials could help to obtain fine and uniform grains and then achieve good signal to noise ratio. In particular, the design of media having good thermally stability, writability, and SNR (readability) is quickly approaching fundamental limits.
However, fundamental limits of the physics underlying the HDD technology make the extension of this trend into the next decade very challenging. Since 2000, amazing improvements have been brought about by the introduction of CoCrPt:oxide-based perpendicular magnetic recording together with very sensitive GMR and TMR sensors. In the current granular media, one bit of information is stored within multiple magnetic grains and the thermal stability of the data is defined by the thermal stability of each grain. HDD technology offers a reliable and low cost solution to storing large amounts of data but future improvements in the development of HDDs introduce a variety of challenges. Thiele, in Comprehensive Nanoscience and Nanotechnology (Second Edition), 2016 5.04.4.4 Summary and Conclusions