Mar 16 2010
To increase the storage density of disk drives beyond their present-day capabilities, scientists need to realize 'giant magnetoresistive' (GMR) spin valves for use in their read heads. A combination of the 'Heusler' alloys Co2CrZ (Z = Si or Al) and Cu2CrAl are shaping up as attractive material components for such devices, owing to work from Viloane Ko and co-workers from the Data Storage Institute of A*STAR, Singapore.
Information in hard disk drives is stored using the orientation of the 'spin' of electrons associated with magnetic atoms on the disk and retrieved by read heads that are sensitive to their orientation.
In GMR spin valve-based read heads of the current-perpendicular-to-plane (CPP) type, a nonmagnetic spacer layer is sandwiched between two ferromagnetic electrodes (Fig. 1). The reference layer's spin is 'pinned' to one direction, whereas the 'free' layer's spin orients according to the direction of the spins it probes on the disk. If the spins in the two layers are parallel to each other, spin-polarized electrons flow easily through the device; if they are antiparallel, however, the resistance is high-hence the term GMR-yielding a sensitive probe of the binary information stored on the disk.
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