Michiaki Kanamine

Spin-valve read heads with NiFe/Co/sub 90/Fe/sub 10/ layers for 5 Gbit/in/sup 2/ density recording

Successful use of a NiFe/Co/sub 90/Fe/sub 10/ bilayer as a soft magnetic free layer in spin-valve films with a GMR enhanced structure comprised of NiFe/Co/sub 90/Fe/sub 10//Cu/Co/sub 90/Fe/sub 10//FeMn is outlined. The GMR ratio of the spin-valve film with Co/sub 90/Fe/sub 10/ is over 7% and the coercivity of the free NiFe/Co/sub 90/Fe/sub 10/ bilayers is less than 5 Oe. A merged inductive/spin-valve head was fabricated with a read track-width of 1.3 /spl mu/m and a read gap-length of 0.26 /spl mu/m using spin-valve film with a Ta(50 /spl Aring/)/NiFe(45 /spl Aring/)/Co/sub 90/Fe/sub 10/(30 /spl Aring/)/Cu(32 /spl Aring/)/Fe/sub 10/(22 /spl Aring/)/FeMn(100 /spl Aring/)/Ta(100 /spl Aring/) structure and 260 /spl Aring/ thick domain control Co/sub 78/Cr/sub 10/Pt/sub 12/ magnet layers. Its read/write performance was tested on a low noise CoCr/sub 17/Pt/sub 5/Ta/sub 4/ thin film disk with an Mr/spl middot/t of 0.41 memu/cm/sup 2/ and a coercivity of 2500 Oe. There is no Barkhausen noise in the readback waveform. The result of the microtrack sensitivity profiles reveals an effective read track-width of 0.8 /spl mu/m. A normalized output for a track-width of 880 /spl mu/Vpp//spl mu/m and D/sub 50/ of 166 kFCI was obtained. Using a PRML channel, a bit error rate of less than 10/sup -8/ was obtained without error correction at a data rate of 3.3 MB/s and at a linear density of 217 kBPI on a thin film disk with an Mr/spl middot/t of 0.72 memu/cm/sup 2/. Thus, 5 Gbit/in/sup 2/ density recording with a linear density of 217 kBPI and a track density of 23 kTPI is possible.

Spin-valve sensors with domain control hard magnet layers

We have fabricated unshielded narrow-track NiFe/Cu/NiFe/FeMn spin-valve sensors with a height of 2 /spl mu/m and a track-width of less than 2 /spl mu/m using CoCrPt hard magnets (4/spl pi/Mr=5500 G, Hc=1000 Oe) as a domain control layer. Barkhausen noise was completely suppressed by a longitudinal biasing field from the CoCrPt layers. The bias state was improved by applying a strong ferromagnetic exchange coupling field of 30 Oe between the free and pinned NiFe layers through a 14 /spl Aring/-thick Cu interlayer. We have also fabricated shielded CoCrPt magnet-biased spin-valve read heads with a track-width of 1.7 /spl mu/m. The heads had no Barkhausen noise and very low crosstalk noise.

NiFe/CoFeB Spin-valve Heads For Over 5 Gbit/in/sub 2/ Density Recording

This paper outlines the successful use of NiFe/(Co/sub 90/Fe/sub 10/)/sub 100-x/Bx (x=5, 10%) for soft magnetic, thermally stabilized spin-valves. The GMR effect in the NiFe/CoFeB spinvalve increases after annealing. The annealing effect of CoFeB on CoFeB/Cu interfaces is investigated by high resolution TEM-EDX analysis. Merged inductive NiFe/CoFeB spin-valve heads with a read gap length of 0.18 /spl mu/m and a write gap length of 0.28 /spl mu/m having NiO(400 /spl Aring/)/NiFe(10 /spl Aring/)/CoFeB/sub 5/(10 /spl Aring/)/Cu(32 /spl Aring/)/CoFeB/sub 5/(20 /spl Aring/)/Ta(100 /spl Aring/) spin-valve film and high Bs laminated FeZrN/NiFe top poles were fabricated. Their read/write performance were tested on a low noise CoCr/sub 19/Pt/sub 5/Ta/sub 2/Nb/sub 2/ thin-film disk with an Mrt of 0.6 memu/cm/sup 2/ and a coercivity of 2600 Oe. A normalized output per track-width of 1000 /spl mu/Vpp//spl mu/m and a 50% rolloff linear density (D/sub 50/) of 182 kFCI is obtained. This performance well exceeds the performance of 5 Gbit/in/sup 2/ spin-valve heads. The measured S/N was 26.8 dB for a spin-valve head with with a narrow read track-width of 0.68 /spl mu/m, and the feasibility of 8 G bit/in/sup 2/ recording density is studied using a 1/7 code Narrow Band PRML channel.

Spin-valves with bias compensation layer

We successfully used a bias compensation layer (BCL) for an improved bias state and asymmetry in spin-valves having a structure of Ta/NiFe/Pd/sub 32/Pt/sub 17/Mn/CoFeB/sub 2//Cu/CoFeB/sub 2//NiFe/Ta/BCL/Ta. The shift of an MR response curve from a zero field is almost zero regardless of the polarity and magnitude of the sense current in an unshielded spin-valve element. Inductive/spin-valve heads were fabricated having trimmed high-Bs electroplated Ni/sub 45/Fe/sub 55/ top poles and a Ta(50 /spl Aring/)/NiFe(20 /spl Aring/)/PdPtMn(200 /spl Aring/)/CoFeB(20 /spl Aring/)/Cu(28 /spl Aring/)/CoFeB(25 /spl Aring/)/NiFe(20 /spl Aring/)/Ta(100 /spl Aring/)/NiFe(30 /spl Aring/)/Ta spin-valve film. Their read/write performance was tested on a CoCr/sub 19/Pt/sub 5/Ta/sub 2/Nb/sub 2/ thin-film disk. The dependence of sense current on the asymmetry was small. Narrow, effective write and read track widths of 0.85 /spl mu/m and 0.62 /spl mu/m were measured, an output of 660 /spl mu/Vpp and D/sub 50/ of 200 kFCI were obtained.

Domain stability of multilayered CoZrCr/Ti stripes

The narrow‐track perpendicular magnetic heads with multilayered CoZrCr/Ti main‐pole films developed here reproduce output signals having increased stability as the number of pairs of CoZrCr layers increases. To see why, a Kerr‐effect apparatus was used to measure the relationship between dynamic domain behavior and the number of pairs of CoZrCr layers for multilayered narrow CoZrCr/Ti stripes of different widths. Increasing the number of pairs of CoZrCr layers suppressed wall displacement and stabilized the domain structure. The domain stability agreed fairly well with the stability in perpendicular heads having multilayered CoZrCr/Ti main‐pole films.

PdPtMn/CoFeB synthetic ferrimagnet spin-valve heads with exchange bias domain stabilization

Reducing the free layer thickness is needed to maintain high field sensitivity in spin-valve heads 1 recording densities over 10 GbiWin2. However, this increaser the readback amplitude asymmeq due to the demagnetizing field Gom the pinned layer and causes the readback instability due to the high field sensitivity of the h e layer. In this paper, \ye describe the fabrication and the excellent readhnite performance of narmw mck-width spin-valve heads with thin free laym. CaFeB/RdCoFeB synthetic fenimagnet pinned layers were used to improve the as-cuy. Domain control was d i d by Copt magneb with exchange bias Fe underlayers.