hamr vs mamr

While Seagate has set a course to deliver a 48TB disk drive by 2023 using heat-assisted magnetic recording (HAMR), Western Digital Corporation has given up on it and is developing a microwave-assisted magnetic recording (MAMR) to push disk drive capacity up to 100TB by the 2030s. Currently hard disk drive use Perpendicular Magnetic Recording (PMR) and Shingled magnetic recording (SMR). PMR technology uses vertically oriented magnetized areas in a disk drive’s recording medium while shingled recording (SMR) writes new tracks that overlap part of the previously written magnetic track, leaving the previous track narrower and allowing for higher track density.

Generally speaking recording is done when grains remain “so-magnetized” until “re-magnetized” by the write head. If we shrink the grain area to increase the areal density of the disk, and hence its capacity, they gradually become unstable, with their magnetism being affected by the magnetic state of their neighbors and temperature changes.

HAMR overcomes the tendency of smaller magnetized areas in current PMR/SMR technology to flip their magnetic polarity, and hence their binary bit value, through temperature changes and interference from neighboring bits.


With HAMR when data is written it is done by applying an laser-induced heat to the grains, which makes it easier to alter their magnetic polarity. However, adding the laser-heating source to the read/write head adds cost, complexity and compromising reliability, longevity and perhaps overall performance.

MAMR uses a different technique to achieve the same thing. It adds microwaves to the write head, using a spin-torque oscillator (STO) to generate them. Electrons in a magnetized areas have a spin state. Applying microwaves at the right frequency causes a resonance effect which can make it easier for the write head’s electrical field to alter the magnetic polarity of the domain.

Advanced Storage Technology Consortium also expect HAMR to result in HDD capacities approaching 50TB early next decade!

According to Western Digital both Seagate and Toshiba will hit a dead end with HAMR so they will introduce MAMR drives in 2019 while Seagate said it has made millions of HAMR drive heads and the technology is reliable. In the coming years we’ll know more about these future technologies as Seagate and Western Digital’s HAMR and MAMR hard drives get closer to reality.

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