Even harmonic ripple effect and demagnetizing field mapping

A new phenomenon in data writing process, named "even harmonic ripple effect," has been reported and investigated in this paper. The analysis and simulation results show that this effect is due to the interpattern proximity effect on the hard transition shifts when a data pattern formed by square wave writing current at a frequency (2n+p)f is overwritten by another square wave writing current at a frequency f, where n is an integer and p is an introduced shift rate. The ripple effect can be used to measure the amount of demagnetizing field fluctuation of magnetic media in magnetic recording system.