Magnetic storage

As noted previously, there are two principal types of magnetic media—hard disk drives (HDDs) and magnetic tapes—both of which we now briefly discuss. 

Hard disk magnetic storage hard drives consist of rigid circular disks with diameters that range between about 65 mm (2.5 in.) and 95 mm (3.75 in). During read and 

For the current HDD technology, magnetic bits point up or down perpendicular to the plane of the disk surface this scheme is appropriately called perpendicular magnetic recording (PMR), and is represented schematically in Figme 20.23. 

The current storage capacities of perpendicular HDDs are in excess of 100 Gbit/in. (10 bit/in. ) the ultimate goal for HDDs is a storage capacity of 1 Tbit/in. (10 bit/in. ). 

Using the plate-shaped barium-ferrite medium, a tape-storage density of 6.7 Gbit/in. has been achieved. For the industry-standard LTO tape cartridge, this density corresponds to a storage capacity of 8 Tbytes of uncompressed data. 

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Gellman A J 1998 Lubricants and overcoats for magnetic storage media Curr. Opinion Colloid Interfaoe Soi.Z 368-72... 

B. Bhushan, Tribology andMechanics of Magnetic Storage Devices, Springer-Vedag, New York, 1990. 

Figure 6 SFM image of a magnetic storage disk demonstrating roughness analysis.

Chemical Engineering Contributions Microcircuits Photovoltaic Devices Optical and Magnetic Storage and Recording Light Wave Media and Devices Interconnection... 

Robertson, J., Requirements of Ultrathin Carbon Coatings for Magnetic Storage Technology," Trihol. Int.,VcA. 36,2003, pp. 405-415. 

Bhushan, B., Tribology and Mechanics of Magnetic Storage Devices, 2nded., New York Springer-Verlag, 1996. 

Langmuir-Blodgett films of iron(III) arachidate have been used as precmsors for the production of ultrathin layers of iron oxide for potential use as magnetic storage media... 

Another area with a large research activity is also related to computer technology. It is electrodeposition of magnetic alloys for thin-film recording heads and magnetic storage media. Here new magnetic materials are needed that have properties superior to those of electrodeposited NiEe (Permalloy). These activities are reviewed by Andricacos and Romankiw (25) and Romankiw (32). 

The magnetic storage media being employed are ternary amorphous alloys lTable 6) composed of the rare-earth elements gadolinium. Gd. and terbium. Tb. with Fe and Co lor use in the near infrared. These materials are compatible with GaAs-bascd lasers. These alloy s arc fcnimagiictic. 

CAUTION No one with a pacemaker should approach within 30 cm of an NMR instrument. Higher specification instruments require further caution. If in doubt, consult a doctor and the equipment manufacturer. Keep magnetic storage devices (including credit cards) away from the measurement coil. 

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