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The first hard disk drive, sold by IBM in 1956 had a capacity of 5 megabytes. Disk drives available today from your local office supply store can hold more than 5 terabytes. This million-fold increase in storage capacity over the past 50 years has been the result of continuous engineering advancements that has increased the areal density with which information can recorded the disk at a rate of about 30% every year. Over the years, scientists and technologists have repeatedly overcome seemingly insurmountable hurdles in achieving such growth. The next great hurdle is the issue of thermal stability: bit volumes are becoming so small that the energy required to reverse the magnetic polarity is on the order of the thermal energy, making the recording unstable. One solution is to increase the energy barrier to reversal (coercivity), but this makes it impossible to record the information using conventional recording heads. This is referred to as the thermal-stability/writeability dilemma in the industry. Several approaches for temporarily reducing the coercivity to allow recording have been proposed, including heat assisted magnetic recording (HAMR) and microwave assisted magnetic recording (MAMR). We have recently demonstrated that acoustic energy can be used to temporarily reduce the magnetic coercivity for recording in a process we call acoustic assisted magnetic recording (AAMR).
In this seminar I will briefly review the magnetic recording process and the looming issue of thermal stability. I will then describe how acoustic waves may be used to lower the coercivity of a magnetic film and show experimental results demonstrating this effect being used to assist in recording information on a disk. Some back-of-the-envelope calculations will show how the physics of surface acoustic waves and magnetostrictive materials provide a possible solution to the thermal-stability/writeability dilemma. Perhaps in the future, presentations such as this one will be recorded on hard disks using a combination of both magnetic fields and acoustic waves.