Towards quantitative electron holography of magnetic thin films using in situ magnetization reversal

An approach based on off-axis electron holography has been developed for quantifying the magnetization in a sample of unknown local thickness with lateral variations in composition. The magnetic field of the objective lens is used to reverse the magnetization direction in the sample without altering its magnitude, thereby enabling phase changes due to magnetization to be separated from those due to thickness and compositional variations. The technique is demonstrated in applications to a lithographically patterned magnetic film on a silicon nitride membrane and a cross-sectional sample containing a magnetic tunnel junction. The importance of dynamical diffraction effects and fringing fields is discussed. (C) 1998 Elsevier Science B.V. All rights reserved.