Arata Jogo

Readout performance of confined-current-path current-perpendicular-to-plane heads

Current-perpendicular-to-plane (CPP) spin valve (SV) films with nano-oxide layers have been developed. The enhancement of giant magnetoresistance by inserting the current confining layer between free and pinned layers was confirmed by the calculation of the current-flow distribution using a finite-element model. For the bottom-type spin valve films with the structure of PdPtMn/CoFeB/Ru/CoFeB/Cu/oxidized CoFeB(t nm)/Cu/CoFeB, MR ratio of 5.0% and RA of 0.6 /spl Omega//spl middot//spl mu/m/sup 2/ were obtained at t=1.2 nm. The merged head using the CPP-SV film with a nano-oxide layer whose MR ratio was 3.2% was fabricated. The magnetic read core width was 130 nm when the physical free-layer width was 100 nm. 0.91 mV/sub p-p/ output voltage was obtained at the sense current of 4.8 mA which corresponds to the average current density of 19 MA/cm/sup 2/.

A Co-SiO

We have investigated a possibility of Co-SiO2 granular material as a current-confining layer of confined current path (CCP) type-current perpendicular-to-plane (CPP) spin valves (SVs). A resistance-area (RA) product can be controlled by a composition and a thickness of the Co-SiO2 granular layer, and it showed a higher controllability compared to a conventional oxidized metal current-confining layer. The CPP-SV with Co-SiO2 granular layer performed at a relatively large MR ratio of 5.7% with a RA of 1 Omegamum2 and showed a potential of 5% with 500 mOmegamum2. This indicates a role of the Co-SiO2 granular layer as a current-confining structure. Although a tolerance to an applied voltage is insufficient at this stage, a granular material as a current-confining layer, such as Co-SiO2 , will open a door to a realization of CPP-SV magnetic recording heads for an ultrahigh-density recording systemIt was confirmed that the confined current paths spin valves (CPP-SVs) employing the Co-SiO2 granular layer as the current confining layer show relatively large magnetoresistance (MR) ratio with higher controllerability compared to those with the conventional oxidized metal layer. We expect that the granular type current confining layer makes artificial fabrication of the CCP-CPP structure possible.

_2

We have succeeded in enhancing the current-perpendicular-to-plane (CPP) magnetoresistance of the synthetic spin-valves by controlling the spin-dependent transport through the synthetic ferrimagnetic pinned layer using impurities. The new pinned layer overcomes the disadvantage of the synthetic pinned layer in CPP spin-valves for the magnetoresistance reduction. The experimental results are well described by our calculations based on the two-current theory. The proposed pinned layer, together with our newly developed magnetoresistive ferromagnetic materials, will be quite effective in producing CPP spin-valve sensors for ultrahigh-density data storage systems.

Granular Material as a New Current-Confining Layer for Current Perpendicular-to-Plane Spin Valves

A pinned layer structure for current-perpendicular-to-plane (CPP) spin valves that enhances magnetoresistance change (/spl Delta/RA) effectively without changing other layers is shown. It was found that spin blocking layers in the pinned layers increase /spl Delta/RA by decreasing the cancellation of the spin-dependent bulk resistance without significant drop of exchange pinning field.