Evacuation, HAMR and MAMR - three ways to increase the capacity of modern HDD to the maximum

    The 2018 IEEE TMRC Conference was held under the banner of innovations in the development of hard drives. In particular, the developers discussed the nuances of such technologies as the thermally assisted magnetic recording HAMR , the assisted microwave recording (MAMR) and the evacuation, that is, the evacuation of air from the hard disk case with its subsequent sealing.

    As for air exhaust, earlier some HDD manufacturers used an alternative to air, filling the space inside the hard disk case with inert gases, in particular, helium. These discs are more expensive than usual, but their capacity is usually greater than the "average temperature in the hospital." Now there is a company that is going to completely refuse to fill the hard disk case with gases. Instead, they will be pumped out, reaching vacuum conditions.

    One of these companies is a technology startup L2 from the USA. Its employees believe that pumping out gases is the future of HDD. In their opinion, working with vacuum will not complicate, but on the contrary, simplify the production of hard disks with a simultaneous increase in their capacity by more than 35%. The recording method used in this case is called perpendicular.

    Why pump air out? Peter Goglia, technical director of L2, says that in vacuum magnetic plates are not subject to corrosion, which favorably affects the durability of the product. In addition, thanks to the new production method, it is possible to abandon the use of lubricants, including the application of carbon coating both on the plates and on the read heads. All this will simplify and speed up the HDD production process. Moreover, as a result of the pumping of gases, it is possible to reduce the distance between the heads and the magnetic plates up to 3-4 nm. In turn, this will allow to increase the density of the magnetic tracks and increase the storage capacity of the drive. Using the two assistive technologies mentioned above will improve the performance of the HDD.

    Over how to increase the recording capacity of hard drives, developers ponder since the advent of this type of drives. The first to fill the HDD with gas was Hitachi Global Storage Technologies in 2012. According to the calculations of experts, since the density of helium is much lower than the density of ordinary air, replacing the second with the first in the HDD reduces the resistance force during the rotation of the mechanical parts of the HDD. Plus, the force of the gas flow generated by the spindles is critically reduced. This means that the plates can be placed closer to each other. The free space can be used to add new plates, which automatically means an increase in the capacity of hard drives.

    You can also increase HDD capacity by reducing the “grain” of the magnet. It is necessary to reduce the size of the magnetic heads. In the second case, there are more problems than in the first. If you reduce the size of the "grain", then it will quickly lose its magnetic properties than in a normal situation. And this means the loss of information and the appearance of errors. The problem can be solved by using in the manufacture of plates of materials with high retention force. But here we have to solve a new problem - the standard HDD head, due to its small size, is simply not able to actively influence the magnetic field of a plate made of this kind of material.

    In this case, HAMR technology is used, which allows the surface of the magnetic plate to be heated in the recording region with a laser. The heating temperature is about 500 degrees Celsius, which leads to a weakening of the holding force. This means that even a low-powered head can magnetize the required “grain” with the necessary force. After the heating point cools, the plate section becomes stable, so it cannot demagnetize just like that.

    It is possible to strengthen the magnetic properties of the head using the MAMR technology, which is based on a magnetic field generator using microwaves. Resonance that occurs during generator operation amplifies the magnetic field of the head. And this allows us to achieve the result - magnetization of the grain of a special plate material, as in the previous case, but without heating.

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