Microwave-assisted magnetic recording (MAMR) is a new technique for increasing the areal density of hard drives, which allows for substantial improvements in data storage capacity. In this article, we’ll provide a basic overview of the technology — and the potential applications of MAMR.
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Microwave-Assisted Magnetic Recording: The Basics
Hard drives store data on a series of platters, which are subdivided into concentric areas called tracks. On a conventional hard drive, the size of these tracks is limited by physics: Hard drives use actuator heads to read and write data, and when tracks are extremely small, the actuator heads cannot perform reliably. This limits the potential areal density of conventional hard drives.
However, manufacturers have found ways to bypass this limitation. By applying heat to the platters during the write operation, the media can become more writable — the tracks can be smaller and closer together. This is known as heat-assisted magnetic recording (HAMR).
While HAMR has been shown to be effective, it requires near-field light, which is generated near the actuator heads. The light heats the platters significantly, which can cause issues for conventional recording medium alloys.
MAMR technology applies microwave and magnetic fields to accomplish a similar effect, but without the potential degradation caused by heating. The microwave fields allow the magnetization of the media (in other words, the write operation) to utilize a much lower magnetic field than is possible with conventional methods. In theory, this allows for greater areal density without degrading the media through the application of heat.
Accomplishing this feat requires several innovations in hard drive design.
Spin Torque Oscillators (STOs)
To generate a magnetic field, the actuator heads of a MAMR drive are equipped with specialized write heads with a spin torque oscillator. The oscillator has a field generation layer and a spin injection layer, which are magnetized to the direction of the magnetic field that exists in the gap between the platters and the write head. Oscillation occurs during the write process, and microwave fields are applied to the media, along with the magnetic fields needed for the write operation.
The primary issue with MAMR technology: Manufacturers must develop a spin torque oscillator that maintains an acceptable oscillation frequency. This oscillator must have a power source that fits within a 3.5-inch hard drive form factor, and must not dramatically increase the cost-per-gigabyte of the product — although with any innovation, the costs will gradually decrease over time.
MAMR Recording Media
To resonate with the oscillating frequency of the microwave, MAMR drives will need to use specialized recording media with balanced layers, each with different (and specific) levels of hardness.
While MAMR hard drives are not widely available, major manufacturers have been working on perfecting the technology. Per recent research, MAMR is a viable option for next-generation storage — as long as engineers can overcome the technical challenges.
The Advantages of MAMR Hard Drives
Currently, the most effective option for extending hard drive areal density is shingled magnetic recording, which allows for extremely high capacities with a consistent 3.5-inch hard drive form factor. We’ve written about shingled magnetic recording in other articles; the bottom line is that “shingling” data has enormous benefits, but can also introduce certain issues with read/write speeds and potentially reduce data integrity (depending on the application and drive design).
MAMR hard drives would not have these limitations. In the future, MAMR technology could allow for hard drive capacities of up to 80 terabytes (TB) — without reducing operating speeds or reliability. Some manufacturers have made plans to introduce MAMR drives as early as 2023 .
Time will tell whether HAMR or MAMR technology becomes the standard for high-capacity hard drives. However, both technologies will be destined for enterprise-level applications when introduced. Most consumers have little use for an 80 TB hard drive, and the new drives are widely expected to be expensive for the first few years after their introduction.
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