Hard Disk Drive as a Magnetomechanical Logic Device

—We consider the conditions how two binary numbers can be superimposed on the same track with the use of different recording magnetic fields. As a result the average magnetization of longitudinal medium along the track can have three states:-M, 0 and +M. Possibility to perform logic operations with these states is considered. We demonstrate OR, AND, XOR and NOT operations and discuss a modification of a recording device. I. INTRODUCTION ARD DISK drive is usually used as just a storage device in personal computers. Here we consider a possibility to perform logic operations on a hard disk drive. This can be done on a magnetic recording medium in which there is a possibility to superimpose binary information. Such media consist of magnetic particles with i) different anisotropy fields and/or with ii) different anisotropy axes orientations. The first is, for example, an oriented (e.g., perpendicular) medium with a distribution of anisotropy fields. The second is typical for a longitudinal medium where the anisotropy axes of particles are distributed randomly. The elementary logic operation consists of three steps: 1) Applying a strong magnetic field, one writes the first binary number A as the transitions between different average magnetization states (–M and +M, all previous information is erased). 2) Using smaller magnetic field that reverses just a part of magnetic particles, we write the second binary number B. Doing so we obtain transitions between 0 and M,-M and 0, and –M and M. 3) The reading sensor detects the peaks of magnetization variation between the uniformly magnetized regions on the recording magnetic surface and gives result of the logic operation OR, AND, XOR or NOT. Using the results of XOR and AND operations, we can construct an adder.