In the beginning of XXI century the HDD manufacturers were under the influence of true euphoria. The transition to GMR-heads promised long-term prospects for further data density increase. All they needed to do was to continue reducing the size of the heads and the bit size in the platters magnetic layer, and they would be set for a long time.
They could report the launch of the new HDD family every 8-9 months, and the maximum storage capacity if the new drives would be 1.5 and maybe even two times higher than what the previous HDD family boasted.
However, this forecast never came true, just as any other long-term forecast. The problem was connected with continuous reduction of the magnetic bit size. The smaller got the bit, the higher was the probability that its magnetic polarity may change spontaneously due to the influence imposed by the magnetic power from the neighboring bits. Since with the current data density one domain contains just a few dozens of bits, then the oscillation of just one single bit may result into an avalanche-like phenomenon. Of course, in this case we should really worry about the data security.
What could be done to eliminate this threat? We cannot cover the plates with higher coercivity material, because in this case we will need to increase the GMR-heads size (because we will need a stronger magnetic field). And this is absolutely impossible, because the adapt density is directly dependent on the magnetic head size.
Is there any way to overcome this super-paramagnetic barrier? Yes, there is!