Spin valve read head

C. Tsang, D. E. Heim, R. E. Fontana, V. S. Speriosu, B.A. Gurney, M.L. Williams Design, fabrication and testing of spin-valve read heads for high density recording, IEEE Trans. Magn. 30, 3801 (1994)... 

Figure 6. Spin-valve sensors (a) Unshielded spin valve sensor schematics, (b) linearized transfer curve for the underbiased, and properly biased sensor, (c) experimental transfer curve for an unshielded spin valve sensor (H.Ferreira, INESC MN), and (d) shielded spin valve sensor used as a read head.

In this section, low resistance tunnel junctions prepared by natural oxidation [42-45] or remote plasma oxidation techniques [46] will be described, since up to now they have provided the lowest junction resistances, required to supplant spin valves for read head applications above 100-200 Gbit/in2. At the heart of tunnel junction fabrication lays the barrier fabrication. For read head applications, in the 100-300 Gbit/in2 region, junction resistance must be around 1 Qpm2 [47-51]. Figure 9(a) shows a TEM micrograph for a 1 nm thick AlHfOx low RA barrier [52],... 

Fig. 5.3-23 Schematic illustration of an IBM GMR spin valve sensor used in read heads. M and M2 are magnetizations,and 0i and 62 are angles from the longitudinal direction. The read head moves perpendicular to the xy plane. (After [3.102])...

Fig. 5. 3-32 Schematic illustration of an MR read head. A spin valve ( aU-metal or MTJ) is used as an ultrasensitive sensor for the very low magnetic field strength generated by the small magnetic domains (bits). When a weak magnetic field, such as from a bit on a hard disk, passes beneath the read head, the magnetic orientation of the free layer changes its direction relative to the pinned layer, generating a change in electrical resistance due to the GMR effect. (After [3.106])...

Han, G. C., et al. A Differential Dual Spin Valve with High Pinning Stability. Applied Physics Letters 96 (2010). Discusses how hard disk drives could include ten terabytes of data per square inch using a new read-write head design. 

To incorporate this technology into a read head, one of the magnets is a hard permanent magnet and the other is a soft magnetic material such as Supermalloy. The information is coded on the disc as domains that are N or S for logical 1 or 0. As the disc moves imder the read head, the spin valve opens and closes depending on the field induced in the soft magnetic head. 

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