GB1385984A - Magnetic data storage - Google Patents

Abstract

1385984 Magnetic transducers PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd 7 July 1972 [10 July 1971 13 April 1972] 31955/72 Heading G5R A transducer comprises a plate which in use supports cylindrical magnetic domains. In a disc pack arrangement described with reference to Figs. 4, 5 (not shown) and Fig. 6, a series of rhombic permalloy dots 16, 17 are vapour deposited on a series of rare earth orthoferrite plates 10 (10<SP>1</SP>, 1011 etc.) to provide stable positions for cylindrical domains produced in the plates (domain producing means not illustrated), and the domains are maintained by a bias field perpendicular to the plates (field producing means not illustrated); currents may then be driven through electrical conductors 18, 19 to produce auxiliary fields which cause the domains to be displaced laterally between " ZERO " positions such as 14 and " ONE " positions such as 15, the recorded areas 21, 22 on the tracks 11, 12 being likewise affected. The domain displacements may be sensed with magneto-resistive strips (23, 24) as described wtih reference to Fig. 8 (not shown). In the embodiment of Fig. 9, a bias field H maintains a domain 39 in a plate 33, a current in conductors 29, 30 produces domain deflection perpendicular to the direction of movement v of the record 34, thereby causing tracks 35 to be formed, and a fluctuating current applied to conductors 31, 32 produces corresponding fluctuations in the tracks 35 as shown in the ringed inset. In a similar embodiment (Fig. 10, not shown) conductors 31, 32 are omitted and the fluctuation (i.e. the signal) is applied to the bias field H to cause the track width to vary. The plate in which the domains are formed may also have a radiation-sensitive magnetic permeability, thereby allowing the domains to be moved by radiation means (not detailed).