Magnetic materials domains

Soft Magnetic For soft magnetic materials, domain wall movement is easy during magnetization Materials and demagnetization. Consequently, they have small hysteresis loops and low energy... 

Ca is replaced by a rare-earth element, resulting in a distorted perovskite stmcture, which is essentially orthorhombic. Orthoferrites, studied extensively in the early 1970s as potential data storage materials based on magnetic bubble domains (10), have been largely replaced by the garnet materials (see... 

Maps of the remanent magnetic domain pattern in the near-surfiice region of magnetic material and thin films can be made routinely. 

On his return home in 1911, Honda was appointed professor of physies at the new Tohoku Imperial University in Sendai, in the north of Japan this institution had been established only in 1906, when the finance minister twisted the arm of an industrialist who had made himself unpopular because of pollution eaused by his copper mines and extracted the necessary funds to build the new university. A provisional institute of physical and chemical research was initiated in 1916, divided into a part devoted to novel plastics and another to metals. This proved to be Honda s lifetime domain he assembled a lively team of young physicists and chemists. In the same year, Honda invented a high-cobalt steel also containing tungsten and chromium, which had by far the highest coercivity of any permanent-magnet material then known. He called it KS steel, for K. Sumitomo, one of his sponsors, and it made Honda famous. 

Magnetic materials can be paramagnetic, ferromagnetic, or antiferromagnetic. In ferromagnetic materials, large domains of electrons have the same magnetic moment. 

There are two principal uses for glassy metals. Because metal glasses have no barriers for domain wall movement they are excellent soft magnetic materials. Thin ribbons have been used for transformer cores since the 1960s. Metallic glasses have very good corrosion resistance and very low damping. 

For a material to be soft magnetically, its domain walls must move easily. The principal obstacles to domain wall movement are inclusions and grain boundaries. Low dislocation contents, residual stresses, and a low interstitial content, are also important. 

A metallic glass containing 80% Fe and 20% B is an excellent soft magnetic material because there are no grain boundaries to obstruct domain wall motion. 

Some of the best hard magnetic materials are those with a hexagonal structure. In these there are only two possible domains, differing by 180°. Table 18.5 lists the maximum BH product for several alloys. Cheap permanent magnets can be made by aligning fine iron powder in a magnetic field while it is being bonded by rubber or a polymer. 

Coercivity and saturation magnetisation parameters are influenced by domain state (and hence by grain size of the magnetic fraction). Domain state in materials where the remanence is dominated by magnetite can be determined by position on a Day plot (Day et al., 1977) on such a plot, stability of remanence increases towards the upper left comer. Samples BC4, RC2, RC3, and RC5, all of which show evidence in their demagnetisation behaviour for the presence of a reversed-polarity component, plot closest to the stable part of the Day plot (Fig. 10). Samples BCl, BC3, BC5, and RCl 1, which do not show a clearly isolated reversed component, plot in less stable positions. Samples RC4 and RCl2, which have complex demagnetisation, plot as outliers, well to the less stable side of the plot. 

Magnetic domain—Microscopic regions of a magnetic material which behave as miniature magnets and control the material s behavior. If they are preferentially oriented, the material is magnetic if they are randomly oriented, the material is non-magnetic. 

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