We have further developed the NIST magnetic imaging reference sample t
o include a magnetic pattern which can indicate the magnetic polarity
of a magnetic force microscope tip. Several samples cut from the same
disk were measured with a single tip. We have also measured a single t
ransition with several tips. Both measurements have shown the variabil
ity in images taken with different tips and different instrument confi
guration which underscores the need for a well calibrated sample.