Junichi Kane

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.

Spin-valve head with specularly reflective oxide layers for over 100 Gb/in/sup 2/

We have developed spin valves with thin oxide reflective layers, which exhibit a greatly improved magnetoresistance (MR) performance while keeping other good properties, such as an exchange bias field of over 1000 Oe and a coercivity and an interlayer coupling field of less than 10 Oe. The giant magnetoresistance (GMR) values reached over 12% for the spin valve with a single specular layer and over 15% for the spin valve with double specular layers. The oxide reflective layers helped improve MR performance due to enhanced specularity at the oxide interfaces. Evidence of enhanced specularity was provided by the observed reduced sheet resistance and oscillatory interlayer exchange coupling between the free layer and the spacer in the spin valve. The observation of the oscillation was possible due to amplified Ruderman-Kittel-Kasuya-Yoshida (RKKY) coupling, as seen in a multilayered superlattice composed of ferromagnetic layers with nonmagnetic spacers. We successfully fabricated read heads by incorporating such spin valves. In particular, very narrow read track width was achieved in the head with double reflective layers. The read track width was estimated to be less than 0.14 /spl mu/m. The head was tested on a low noise CoCrPt-based alloy disk with a coercivity of 3170 Oe and an areal moment of 0.36 memu/cm/sup 2/. The head showed a normalized output of 8.6 mV//spl mu/m with an asymmetry of 0.5% at 2 mA sense current, a /spl sim/40% increase over that of the head with a single reflective layer that was used in the demonstration of 56.1 Gb/in/sup 2/. We have therefore demonstrated that our head with the specular layers can be used for an areal density of over 100 Gb/in/sup 2/ in magnetic recording with the help of advanced media and integration techniques.

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.

Effect of thin oxide capping on interlayer coupling in spin valves

We controlled interlayer coupling from ferromagnetic to antiferromagnetic by appropriately capping spin valves with thin oxides. The interlayer coupling field was -16.6 Oe at a Cu-spacer thickness of 30 /spl Aring/. The sign of coupling changed at a Cu-spacer thickness of 20 /spl Aring/. The antiferromagnetic coupling achieved in this way allowed a reduction of thickness of the Cu spacer down to 20 /spl Aring/ without loss of good magnetic and electrical properties, and this led to a significant improvement in the MR response of the spin valves. The interlayer coupling field was only +8.6 Oe even at a Cu-spacer thickness of 20 /spl Aring/. We attribute the improvement in MR response to less current shunting through the most conductive Cu layer and to enhanced specular scattering at the interface between the free and the oxide capping layer.

Write heads with pole tip consisting of high Bs FeCoAlO films

We investigated the magnetic properties, corrosion resistance, and microstructure for the sputtered FeCoAlO films, and the properties of write heads that use them for pole tips. The FeCoAlO films have soft magnetic properties as well as magnetic induction Bs /spl sim/ 2.2 T, which is equal to the Bs of pure-Fe. In-plane uniaxial anisotropy for the as-made films is almost unchanged though a magnetic field is applied during annealing, i.e., the magnetic annealing effect is negligible. The films have sufficient magnetic thermal stability and corrosion resistance to withstand magnetic head fabrication processes. For write heads with pole tips which consist of FeCoAlO films, the overwrite (O/W) and the nonlinear transition shift (NLTS) show about -35 dB and 13%, respectively. Therefore, these FeCoAlO films can be advantageously applied to writing heads.

Magnetic and electrical properties of spin valve with single and double specular oxide layers

Appropriate oxide capping on a spin valve significantly improved electrical and magnetic properties. The interlayer exchange coupling oscillated in the thickness range of a Cu spacer (between 20 and 30 A). The coupling was antiferromagnetic and it allowed us to reduce the Cu spacer down to 20 A without sacrificing the good properties of the spin valve. The improvement is due to enhanced specular reflection at the interface between the magnetic and the oxide layer and to less current shunting through the Cu spacer. In particular, the Cu in the capping acts as a filter controlling the diffusion of oxygen, which has led to the soft magnetic properties. Embedding an additional thin oxide layer into the pinned layer further improved the magnetoresistance response of the spin valve. Confinement of electrons between two oxides helps increase the occurrence of spin-dependent scattering. As a result, high giant magnetoresistance values resulted. The coupling oscillated from ferromagnetic to antiferromagnetic as a ...

Thermal deterioration mechanism of CoFeB/PdPtMn spin valves

We clarified the mechanism of thermal deterioration that occurs in the CoFeB/PdPtMn spin-valve films at temperatures above 310 °C. Two kinds of CoFeB spin-valve film, Ta/NiFe/CoFeB/Cu/CoFeB/PdPtMn/Ta (B:0–3 at. %) and Ta/NiFe/CoFeB/Cu/CoFeB/FeMn/Ta (B:2 at. %), were prepared and annealed in a magnetic field. For the PdPtMn spin-valve samples, the magnetoresistance (MR) output decreased after annealing at a temperature above 330 °C and there was an increase in the interlayer coupling field of free and pin layers (Hin). There was no large change in the sheet resistance for annealing below 330 °C. For CoFe/PdPtMn(no B) spin valves, the MR output decreased during annealing at more than 310 °C and there was an increase of Hin. An addition of only 1 at. % of boron into the free and pinned layers is sufficient to obtain thermal stability. For the CoFeB/FeMn spin-valve samples, the MR output decreased for annealing above 280 °, the sheet resistance increased, and the Hin value did not change for annealing below 3...

MR response of PdPtMn/CoFeB synthetic ferrimagnet biased spin-valves

The magneto-resistance responses of the spin-valve films with a very thin antiferromagnetic layer and a synthetic ferrimagnet trilayer as the pinned layer were investigated. Their effective pinning field increased with a decrease in the difference in the thickness of each pinned layer. The MR responses were examined by calculating the surface energy density and the direction of magnetization.

PdPtMn/CoFeB synthetic ferrimagnet biased spin-valves

Spin-nlve heads with a narrower read-gap and thinner spin-valve film are necessary for achieving higher m p & c recording densities in harddisk drives. PdRMn with an ordered Cu-Au-I type srmcNre has B high blocking tempaature and high corrosion resistiviiy which are very attractive for spin-valve hcads[l]. However. a PdPtMn layer thidmess, twm p k r than 200A is essentially required for attaining an exchange pinning field rl, of 6lM Oe. Spiuvalves with synlhetic ferrimagnet hilayers as thc pi& layer have a higher H, and small readback amplitude aseven at very low clement height in ~nparim with a conventional spin-valve[Zl. In this p a p . we repat on lhe MR response of CoFeBKWCoFeB syutaic ferrimagnn biased spin-valve (ferri-SV) films with PdPtMn a m i f m p e r and present the success^ redunion oft-. to 8oA.