The Method of Storing Data on Array of Ferromagnetic Microwires Based on Magnetic Hysteresis Evolution
Arrays of ferromagnetic microwires are proposed to be used for data storage with potential application in labelling. Each microwire can be controllably annealed with flush current pulse, which produces a permanent change in the magnetic structure. Depending on the current pulse magnitude and duration a specific magnetic anisotropy is induced in a selected microwire resulting in a change in a hysteresis curve. This permanent change in hysteresis which could be remotely detected is ascribed to an information bit. For experiment, a glass-coated microwire of Co71Fe5B11Si10Cr3 composition with a total diameter of 29.5 μm and a core diameter of 23.9 μm was used. The wire is characterized by a small positive magnetostriction and bistable magnetic behavior in as-cast state. Current annealing produces both short-range order relaxation and magnetic- field induced circular anisotropy, consequently releases some frozen-in stresses and improves soft magnetic properties. Then, the magnetization loop is inclined and the harmonic spectrum of the voltage pulse generated during remagnetization changes. We have demonstrated the possibility of writing base two number (binary) and base 16 number (HEX) systems. Logic “0” state has been achieved by passing 105mA current for the duration of 700ms while the wire in as-cast state represents logic “1” state. In order to realize multilevel storage, different current pulses (pulse time between: 200 to 700 ms , magnitude- 105 mA) have been passed through an individual wire in the array as shown in the diagram.