G Hembree

Investigations of magnetic microstructures using scanning electron microscopy with spin polarization analysis

Abstract A field emission scanning electron microscope was fitted with electron spin polarization analyzers in order to image submicron magnetic microstructures. Spin polarization analysis of the emitted secondary electrons provides a direct measurement of the magnitude and direction of the magnetization in the area probed by the incident electron beam. The polarization measurement is independent of topographic contrast which is measured simultaneously. The polarization was measured using a new type of analyzer which is very compact, simple, and at least as efficient as a Mott detector. The small detector size allowed the use of multiple orthogonal detectors so that all three components of the magnetization vector could be measured. This apparatus was used to examine the domain structure of various Fe-3% Si crystals.

Scanning electron microscopy with spin polarized electrons (invited) (abstract)

The recent joining of scanning electron microscopy and electron spin polarization analysis has greatly improved the ability to study magnetic microstructure.1,2 By measuring the spin polarization of secondary electrons, scanning electron microscopy with polarization analysis (SEMPA) can directly measure the magnitude and direction of the magnetization and direction of the magnetization in the region probed by the incident electron beam. This region is defined by the diameter of the incident electron beam (∼10 nm) and the escape depth of the secondaries (∼5 nm). In addition to the purely magnetic image SEMPA also simultaneously and independently measures the usual topographic image, thereby making comparisons between magnetic and topographic structures easier. We have successfully used SEMPA to study magnetic structures in Fe crystals, permalloy films, CoNi recording media, and metglasses. Examples from this work will be given in order to demonstrate the unique capabilities of SEMPA.

Magnetic microstructure of amorphous alloys studied using scanning electron microscopy with polarization analysis (abstract)

The recent development of scanning electron microscopy with polarization analysis (SEMPA) has made the direct measurement of magnetic structures with submicron spatial resolution possible.1,2 Because the secondary electron spin polarization is proportional to the magnetization in the area probed by the incident electron beam, the magnetization is measured directly, independent of topographic contrast. Topographic images are measured simultaneously, however, permitting comparisons between magnetic and structural properties. In addition the use of multiple, orthogonal detectors permits measurement of the magnetization magnitude and direction. We have recently used this technique to look at various Fe‐rich amorphous ferromagnetic alloys. In particular SEMPA was used to examine the rotation of the magnetization within domain walls and to study changes in magnetic microstructure due to Ar ion bombardment and annealing.