Magnetic Domain Observation of Ferrites by SEM and Its Applications

Abstract

The magnetic domain observation techniques using Scanning Electron Microscopy (SEM) is applied on the research of Mn-Zn ferrite materials. Scratching along [010] direction on (001) plane induces a local magnetic anisotropy parallel to [100] direction around scratch groove. Surface damage by abrasive processes causes a heavy influence on magnetic domain structure, which reaches to 300μm deep from the surface. The surface damage induced domain structure consists of fine 180°C walls array vertical to surface and zig-zag shaped 90°C walls. The reversible 180°C and 90°C domain walls displacements can be observed during continuous change of applied external force even as small as 0.7 N. Dynamic observation of 180°C domain wall displacement is also possible and the suppression of wall displacement can be observed at 60 kHz under 16 A/m magnetic field. The magnetic domain structure of combined crystal-structured ferrites is also investigated and a joint boundary between single- and polycrystals is revealed strain free.