Dependence of thermo-magnetic mark size on applied STM voltage in Co/Pt multilayers

Summary form only given. We present characterization of a magnetic recording process potentially suitable for proposed probe-based storage systems. A scanning tunneling microscope (STM) is used to locally heat a uniformly magnetized perpendicular recording medium. In this work, a 10 nm thick Co/Pt multilayer thin film was used as the recording medium. Pulsed heating of the medium was done using the STM mode of a DI Nanoscope III. Detailed measurement of mark size vs. pulse amplitude (tip-sample spacing controlled at 20 mV bias and 2 nA of tunneling current) shows a relatively constant mark diameter of about 220 nm (theoretical calculation shows the minimum stable domain size for Co/Pt is /spl sim/100 nm), when the voltage is above a threshold of 2 V. This result contradicts previous results by J. Nakamura et al. (see J. Appl. Phys., vol. 77, p. 779-781, 1995), which showed increasing mark size with increasing applied voltage. By using a model of field emission from an STM, we suggest this discrepancy is due to the change in tip-sample spacing during writing due to reaction of the mechanical system. The threshold phenomenon may be due to the threshold of domain nucleation and breakdown current to follow through.