MEASUREMENT OF THE STRAY FIELD EMANATING FROM MAGNETIC FORCE MICROSCOPE TIPS BY HALL-EFFECT MICROSENSORS

We describe the use of micronic Hall sensors as magnetic-field profilo meters with submicron resolution. The procedure involves the deconvolu tion of Hall voltage maps produced by scanning the field source over t he sensor, with a scanning probe microscope. The response function of an infinite Hall cross is calculated analytically in the two-dimension al case, using conformal mapping techniques. Various methods of deconv olution of the Hall voltage maps are presented and compared. The calcu lated response function is used for the deconvolutions, and different effective sensor sizes are tried. It is shown that the remaining main uncertainties come from the ignorance of the true response function of the sensor, ascribed to the charge depletion phenomenon that is known to occur at the sensor edges. The method is applied to thin-film magn etic force microscope tips for which a precise knowledge of the tips f ield at sample location proves crucial to image interpretation. Maximu m fields in the range 10-100 Oe are found at a distance known to be ab out 100 nm from the tip contact surface, depending on the tip coating thickness and magnetization direction, (C) 1997 American Institute of Physics.