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Volume 95, Issue 3, 01 February 2004
- APPLIED PHYSICS REVIEWS - FOCUSED REVIEW
95(2004); http://dx.doi.org/10.1063/1.1633979View Description Hide Description
Experimental results on the characterization of commercially available magnetic force microscopy(MFM)thin film tips as a function of an external magnetic field are presented. Magnetic stray fields with a definitive z-component (perpendicular to the substrate) and a magnetic field strength of up to are produced with current carrying parallel nanowires with a thickness of which are fabricated by electron-beam lithography. The magnetic fields are generated by electrical dc-currents of up to ±6 mA which are directed antiparallel through the nanowires. The geometry and the dimensions of the nanowires are systematically varied by choosing different wire widths w as well as separations b between the parallel wires for two different sets of samples. On the one hand, the wire width w is varied within while the separation between the wires is kept constant. On the other hand the separation b between the parallel wires is varied within while the wire width is kept constant. For all the geometrical configurations of parallel wires the resulting magnetic contrast is imaged by MFM at various tip lift-heights. By treating the MFM tip as a point probe, the analysis of the image contrast as a function of both the magnetic field strength and the tip lift height allows one to quantitatively determine the effective magnetic dipole and monopole moments of the tip as well as their imaginary locations within the real physical tip. Our systematic study quantitatively relates the above point-probe parameters to (i) the dimensions of the parallel wires and (ii) to the characteristic decay length of the z-component of the magnetic field of parallel wires. From this the effective tip-volume of the real thin film tip is determined which is relevant in MFM-imaging. Our results confirm the reliability of earlier tip calibration schemes for which nanofabricatedcurrent carrying rings were used instead of parallel wires, thereby proving that the tip calibration equations depend on the underlying stray field geometry. Finally, we propose an experimental approach which allows one to measure the magnetization of nanoscale ferromagnetic elements with an in-plane orientation of the magnetization, quantitatively, by using a calibrated MFM-tip.