Magnetic domain structure

The second mode of operation is the non-contact mode, in which the distance between tip and sample is much larger, between 2 and 30 nm. In this case one describes the forces in terms of the macroscopic interaction between bodies. Magnetic force microscopy, in which the magnetic domain structure of a solid can be imaged, is an example of the non-contact mode operation. 

It is also interesting to point to the so-called gyromagnetic effect, observed in Fe-Si-B amorphous wires with a particular magnetic-domain structure (Chiriac et al. 2000b). 

Explain why it is that magnetic domain structures in a thin magnetic garnet layer can be visualized in a polarizing microscope and how the various structures can be exploited. Describe two routes for fabricating such layers. 

FIGURE 8.2 Schematic picture of magnetic domain structures of magnetic particles (a) superparamagnetic (b, c) single-domain (d) two-domain and (e) multidomain particle. 

Saito N, Fujiwara H, Sugita Y (1964) A new type of magnetic domain structure in negative magnetostriction Ni-Fe films. J Phys Soc Jpn 19 1116-1125... 

Because the electron phase shift is produced not only due to magnetic fields but also due to changes in the specimen thickness, magnetic lines of force can be directly observed through an interference micrograph only for specimens whose thickness is uniform. A three-dimensional magnetic domain structure therefore cannot be determined Irom an interference micrograph. 

Fig. 2.10. Schematic diagram of the magnetic domain structure in a cobalt particle.

The correlation of magnetic properties with structure was shown for Dy thin films on W(llO), too [166]. This system was additionally investigated with emphasis on the influence of structural defects like line defects [167] and dislocation cores [168] on the magnetic domain structure. 

Effects of Co layer thickness and external magnetic field on the magnetic domain structure are studied. Bubblelike domain structures were created applying a magnetic field perpendicular to the sample plane. A decrease of the domain size was observed applying the in-plane field. 

In present work we study the magnetic domain structure of cobalt film near SRT and the influence of an external magnetic field on it by MFM. 

The MFM images of the magnetic domain structure of Co film for different Co thicknesses are shown in Fig. 1. Image analysis based on the implementation of autocorrelation function gives the following magnetic domain periods 1.60 nm Co - 5.4 pm, 1.67 nm Co - 3.3 pm, 1.74 nm Co - 2.0 pm, 1.80 nm Co - 0.7 pm, which are in qualitative agreement with the predictions [2]. Besides, it should be noted that domain structure has no preferential direction. 

When secondary electrons are emitted from a magnetic material they become polarised and so by using a polarisation sensitive detector such as a Mott detector to collect the secondary electrons an image can be obtained that has magnetic contrast, allowing magnetic domain structures to be studied. This technique is known as scanning electron microscopy with polarization analysis (SEMPA). 

Ratajczak and Labedzka (1977) and Ratajczak and Goscienska (1979,1980) studied the anomalous Hall hysteresis loops in the vicinity of Tcomp for flash-evaporated films. They showed the relation between magnetic domain structures and hysteresis loops at Tcomp- They explained the anomalous configurations in terms of film homogeneity and the magnetization reversal process. They propose a model of change in film composition and reject the one of magnetic... 

There are many different ways to image magnetic domain structures in a material. All the microscopy techniques we described in Chapter 10 can be used, although, in some cases, deviations from the usual operating procedure are necessary to obtain the desired images. It is also possible to use X-ray topography to study magnetic domains. In this section, we will briefly describe three techniques the oldest, one of the newest, and the trickiest. 

Without question the results summarized here afford just a first glimpse of a rich field in which the magnetism of epitaxial films responds in an interesting and sensitive manner to the epitaxial constraint. The actual state of strain in this limit depends on both the film thickness and the growth conditions. In turn the magnetic state must depend on the state of strain and other factors that may influence, for example, the magnetic domain structure, in addition to the natural variables of field and temperature. An eventual complete description must include the statistical behavior of the spin-slip system. 

It is interesting to observe the influence of a magnetic field on k in the presence of the specific magnetic domain structure typical for the magnetism/superconduction coexistence region. Anomalous behaviour of k in a magnetic field has been observed in TmRh4B4 (fig. 114) ... 

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