Junzo Toda

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.

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.

A thin film head for perpendicular magnetic recording

The effects of main pole thickness and depth on performance of a thin-film head, adopting an amorphous Co-Zr film as the main pole, are reported. Heads with main pole thicknesses Tm of 0.2, 0.3, and 0.5 ¿m, and depths Dp of 2, 5, 10, and 15 ¿m, were constructed, and mounted on flying sliders. Recording and playback were performed using Co-Cr disk media, and it was found that the write/read characteristic depended only slightly on the main pole depth Dp. A head with main pole thickness 0.2 ¿m was capable of high density recording, with a D50 value of 70 kFRPI.

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.

Flux-guided MR head for very low flying height

Our flux-guided magnetoresistive-read/inductive-write composite head, which we named the WING MR head after the shape of its wide flux-guides, is designed for very low flying height or contact recording. It has 0.05 /spl mu/m-thick NiFe single layer flux-guides. The flux-guides are rectangular and wider than the read width. Test results show high linear density resolution and good offtrack characteristics at a flying height of 0.03 /spl mu/m. The wide flux-guides reduce Barkhausen noise without lowering offtrack performance. >

Writer pole remanence of a tapered main pole head

We used a micromagnetic model to study the head remanence of a perpendicular tapered main pole head. To reduce the head pole tip remanence, a single magnetic domain structure forming a vortex state from the pole tip to the tapered region is preferred. A tapered main pole structure with a trailing gap depth less than about 30 nm and a tapered angle (TGθ) equal to about 30° improved the writing efficiency. This was achieved with a head field value more than 1.3 times higher and with a head field gradient about 1.15 times higher than that of the conventional structure. Moreover, the pole tip remanence was reduced to a value closer to that of the conventional structure. The reduction in the throat height had less effect on the reduction in the head remanence in the tapered head than in the conventional head. We also discuss both single pole heads and shielded heads.

Control of asymmetry of spin valve heads based on micromagnetic analysis

Relationship between the asymmetry of spin-valve heads and various parameters is revealed by systematical investigations of a micromagnetic analysis. We design spin-valve heads with a good asymmetry by canting the pinned layer. However, for spin-valve heads for high density recording over 10 Gb/in/sup 2/, a poor asymmetry caused by the degeneration of the magnetization direction of the free layer becomes a serious problem. To solve this problem, we introduce a bias compensation layer (BCL) to the spin-valve structure. We prove that BCL is very effective in controlling the asymmetry.