OBSERVATION OF THE SWITCHING FIELDS OF INDIVIDUAL PERMALLOY PARTICLES IN NANOLITHOGRAPHIC ARRAYS VIA MAGNETIC FORCE MICROSCOPY

A technique has been developed for measuring the switching fields of individual sub-micron magnetic particles using a magnetic force microscope (MFM) in which an in situ magnetic field can be applied. This allows the study of the evolution of the particles' magnetic states as a function of applied field and the direct observation of cooperative switching. Observations of the switching fields for individual nanolithographic permalloy particles are compared with remanent magnetization data, taken with an alternating gradient magnetometer (AGM), on both isolated and interactive arrays of these particles. Comparison of MFM images of the particles with numerical simulations has provided insight into the magnetic behavior of the sensing tips.