Cobalt high coercivity

Vaz MGF, Cassaro RAA, Akpinar H, Schlueter JA, Lahti PM, Novak MA. A cobalt pyrenylnitronylnitroxide single-chain magnet with high coercivity and record blocking temperature. Chem Eur J. 2014 20 5460-5467. 

PiUai, V, Shah, D.O. Synthesis of high-coercivity cobalt ferrite particles using water-in-oU microemulsions. J. Magn. Magn. Mater. 163, 243-248 (1996)... 

Soft magnetic materials are characterized by high permeabiUty and low coercivity. There are sis principal groups of commercially important soft magnetic materials iron and low carbon steels, iron—siUcon alloys, iron—aluminum and iron—aluminum—silicon alloys, nickel—iron alloys, iron-cobalt alloys, and ferrites. In addition, iron-boron-based amorphous soft magnetic alloys are commercially available. Some have properties similar to the best grades of the permalloys whereas others exhibit core losses substantially below those of the oriented siUcon steels. Table 1 summarizes the properties of some of these materials. 

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. 

Pigments treated with only small amounts of cobalt (0.5-1 wt % Co, coercive field strength ca. 31 kA/m) are used as an alternative to cobalt-free y-Fe203 pigments for high-quality, low-bias audio cassettes. The other parameters described in Section 5.1.1 are also of importance for cobalt-treated pigments. 

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