| AVS 54th International Symposium | |
| Magnetic Interfaces and Nanostructures | Wednesday Sessions |
| Session MI-WeA |
| Session: | Nanomagnetic Imaging and Spectroscopy |
| Presenter: | S.H. Liou, University of Nebraska |
| Authors: | S.H. Liou, University of Nebraska L. Nicholl, University of Nebraska R. Zhang, University of Nebraska L. Yuan, National Institute of Standard and Technology D. Pappas, National Institute of Standard and Technology B.S. Han, State Key Laboratory of Magnetism, China |
| Correspondent: | Click to Email |
Selecting an appropriate probe for the sample type is important when imaging magnetic domains using magnetic force microscopy (MFM). We have developed a process for fabricating probes with L10 phase FePt that can image the domain structure of both hard and soft magnetic materials. Commercially available batch fabricated probes with micromachined tips are coated with 5 nm to 30 nm of FePt. After annealing at 650 oC for 1 hour to obtain the L10 phase, the probes are magnetized in a SQUID along a direction 100 from the z-axis. This produces tips with a magnetization direction perpendicular to the sample surface. The resolution of an MFM image is related to the tip-sample distance, which is less than 20 nm for high resolution images. At these distances, the stray field of a hard magnetic sample can be large enough to alter the magnetization direction of the tip, unless the tip has a high coercivity. With our technique, we produce tips with coercivities greater than 1 T—which, as we will demonstrate in this work, is suitable for imaging the domain structure of permanent magnets. Imaging soft magnetic materials presents a different problem; namely, if the stray field of the tip is larger than the coercivity of the sample, the tip will alter the domain structure of the sample—especially at the lift heights necessary for high resolution images. Our process produces tips with a stray field low enough for imaging the domain structure of soft magnetic materials at lift heights less than 20 nm. We have tested our tips on an array of NiFe dots in the vortex state; each element in the array having a diameter of around 600 nm. Since the center of the vortex is easy to move, the stray field from the tip must be small in order to obtain images with an unperturbed vortex center. In this work, we will show images of the dots with an undisturbed vortex in the center of each dot. These results show that our probes are suitable for imaging both hard and soft magnetic materials.