Thin magnetically hard films

The hard disk of a computer exploits thin magnetic metal films with a present-day data storage capacity of about 10 Gb in-2 whereas in the case of flexible tape memory systems incorporating magnetic particles the capacity is about 100 times smaller. 

Gao, C. Lee, Y. C. Chao, J. Russak, M. Dip-Coating of Ultra-Thin Liquid Lubricant and Its Control for Thin-Film Magnetic Hard Disks. IEEE Trans. Magn. 1995, 31, 2982-2984. 

Ferrites can be classified according to crystal stmcture, ie, cubic vs hexagonal, or magnetic behavior, ie, soft vs hard ferrites. A systematic classification as well as some appHcations ate given in Table 1 (see also Magnetic materials, bulk Magnetic materials, thin film). 

The structures of electroplated hard alloys have been less extensively studied than those of similar electrolessly deposited materials. Sallo and co-workers [118-120] have investigated the relationship between the structure and the magnetic properties of CoP and CoNiP electrodeposits. The structures and domain patterns were different for deposits with different ranges of coercivity. The lower-f/c materials formed lamellar structures with the easy axis of magnetization in the plane of the film. The high-Hc deposits, on the other hand, had a rod-like structure, and shape anisotropy may have contributed to the high coercivity. The platelets and rods are presumed to be isolated by a thin layer of a nonmagnetic material. 

The devices are further claimed to ensure that magnetically treated water keeps minerals in a soft amorphous powder form instead of the usual hard crystalline structure. This amorphous powder deposits a thin film of aragonite talc on the inside of pipes and the waterside of condensers which prevents free oxygen in the water from attacking the metal surfaces. ... 

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