Magnetic imaging

In this section, two recently developed magnetic imaging methods are described scanning electron microscopy with polarisation analysis, or SEMPA, and magnetic force microscopy, or MFM. 

SEMPA is based on the same technique as scanning electron microscopy a beam of electrons is focused on the surface of the sample as a result of their interaction with the surface atoms, secondary electrons are emitted an image is then obtained from these electrons. The important difference is that, in ferromagnetic samples, the secondary electrons preserve their 

The magnetic structure in ferromagnetic materials can be imaged by the magnetic version of AFM, the magnetic force microscope, MFM. In this instrument, the cantilever has a ferromagnetic, single-domain tip and 

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Fig. 9 Behavior of [C10mim][FeCl4] (left) and [PRJ[FeCl4] (right) ionic liquid droplets in water when exposed to a Nd2Fe14B magnet. Image adapted from [187]. Image Copyright Royal Society of Chemistry (2008). For color image see online version...

Oil content determination is usually performed by Soxhlet solvent extraction this usually takes up to 4h, but it is the standard method recommended by the AOAC. On the other hand, a method called Foss-Let takes only 5-10 min to determine the fat content in meat products. The typical error associated with this method is reported to be less than 1% when compared to the standard AOAC method (Kroff, 1984). Several other methods of fat analysis include nuclear magnetic imaging (NMI) and electronic meat-measuring equipment (EMME), which can be used for measuring the fat content in lean meat at an accuracy of 0.1%-0.2% of the official method (Kroff, 1984). It functions on the basis of the difference in electrolyte components of lean and fat components. Another method is the Vico-fat measuring system, which uses a perchloroethylene agent (Pettinati, 1982) and the HSI technique. Some of these techniques are rapid and amenable to online, real-time control. 

When used for element specific magnetic imaging PEEM is sensitive to all three components of the magnetisation. 

Magnetic imaging is limited to use at synchrotron radiation facilities because of the requirement for circularly polarized X-ray beams. 

NCGA National Computer Graphics Associa- NMI nuclear magnetic image... 

Volume 36. Magnetic Imaging and its Applications to Materials Edited by Marc De Graef and Yimei Zhu... 

Figure 16.43 Electromagnetic methods for imaging of damage or defects in composite materials, (a) Electric imaging of a GERP sandwich specimen showing the detection of a zone with missing foam (h) magnetic imaging of a delamination in CFRP plate [100].

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