Magnetic domain wall contrast under zero domain contrast conditions in spin polarized low energy electron microscopy

Direct visualization of magnetic domain wall motion in Nd-Fe-B magnets by alternating magnetic force microscopy using Co-GdOx superparamagnetic tip

Probing the dynamic magnetic domain of permanent magnet materials under an external AC magnetic field using magnetic force microscopy is challenging as well as important to reveal their pinning sites and local magnetization processes. In this work, we develop alternating magnetic force microscopy (A-MFM) with a Co-GdO_x superparamagnetic tip for observing the dynamic magnetic domain wall (DW) motion in a, b plane Nd-Fe-B sintered magnets by stimulating the magnetization of the superparamagnetic tip and Nd-Fe-B sample using an external AC magnetic field. This method enables the simultaneous measurement of DC and AC magnetic fields from the sample surface. The measurement results reveal that the DW motion does not happen until the amplitude of the external AC magnetic field reached 77 Oe_0-p (zero to peak). Further increasing the external AC magnetic field strength leads to DW motion with larger movement area and stronger AC magnetic field originating from the DW motion. In addition, A-MFM images shows the pinning sites of the DW motion. The present work provides a direct and effective approach to studying the local dynamic magnetization processes of the magnetic materials on the nanometer scale.

Magnetic Materials and Systems: Domain Structure Visualization and Other Characterization Techniques for the Application in the Materials Science and Biomedicine

Magnetic structures have attracted a great interest due to their multiple applications, from physics to biomedicine. Several techniques are currently employed to investigate magnetic characteristics and other physicochemical properties of magnetic structures. The major objective of this review is to summarize the current knowledge on the usage, advances, advantages, and disadvantages of a large number of techniques that are currently available to characterize magnetic systems. The present review, aiming at helping in the choice of the most suitable method as appropriate, is divided into three sections dedicated to characterization techniques. Firstly, the magnetism and magnetization (hysteresis) techniques are introduced. Secondly, the visualization methods of the domain structures by means of different probes are illustrated. Lastly, the characterization of magnetic nanosystems in view of possible biomedical applications is discussed, including the exploitation of magnetism in imaging for cell tracking/visualization of pathological alterations in living systems (mainly by magnetic resonance imaging, MRI).