Magnetic Field Strength Measurements in Heat-Assisted Magnetic Recording

A method for measuring the magnetic field strength of the magnetic writer used in heat-assisted magnetic recording (HAMR) is presented. The measurement, termed write current assist percentage (WCAP), compares the laser current needed to erase a narrow data track (a micro-track) with the laser current needed when the magnetic writer is assisting with the erasure. The difference is related to the temperature difference in the recording medium. If the temperature dependence of the medium’s magnetic anisotropy is known, the erasure field can be determined. The method is useful for comparing the magnetic response of different write pole geometries, for comparing frequency responses of different designs, and for comparing media.