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Read heads using current-perpendicular-to-plane (CPP) giant magnetoresistance sensors have been fabricated and tested under highdensity recording conditions. A magnetoresistance of 5.5% and shield-to-shield spacing of 45 nm have been achieved by using an all-metal single-spin-valve with Heusler-alloy-based free and reference magnetic layers. Read heads with magnetic read widths ~45 nm were tested on perpendicular media, resulting in signals above 1 mV and signal-to-noise ratio ~30 dB. Linear densities in excess of 1050 kbpi were achieved with thermal fly-height control, compatible with recording areal densities of ~ 400 Gb/in (2). Current-induced spin-torque effects in the recording head were observed to result in rapid performance degradation above a threshold bias voltage of about 75 mV, corresponding to current densities > 10 (8) A/cm (2). Index Terms--CPP-GMR, magnetic recording, read-head, spin-valve.

The magnetics and magnetotransport of current perpendicular to the plane (CPP) giant magnetoresistive (GMR) spin valves utilizing thin CoPt hard magnet pinning layers on Cr seed layers are investigated. Free layer softness does not suffer from the proximity to the CoPt hard magnet due to the relatively thick spacer layers compatible with CPP GMR sensors.

Research into thermally assisted decay of pinning in polycrystalline exchanged biased systems is presented. It is concluded that thermally activated reversal of the pinned layer is a factor in the design of spin valves. The decay rates at operating temperatures are sufficiently large to totally destabilize the pinned layer over the lifetime of a sensor.

In thin film magnetic field sensors, strains adversely affect the gain and bias conditions. A new linear field sensor combining two matched spin valve elements is described. The difference signal from these two elements measures the strain at the field sensor and the sum signal, with the difference as input, gives a strain-compensated measure of the field.

Magnetic recording read heads have been fabricated and tested using a dual-spin-valve (dual-SV) current-perpendicular-to-plane (CPP) giant magnetoresistive (GMR) sensor stack. Thin IrMn antiferromagnetic layers are used for top- and bottom-pinned layers, resulting in a total sensor stack height of 50 nm. Operational read heads with physical sensor trackwidths ranging from 60 to 30 nm have been achieved. Successful readback testing is obtained using perpendicular recording media, with observed magnetic read widths as low as 46 nm. Index Terms--Current-perpendicular-to-plane (CPP) giant magnetoresistive (GMR) read heads, dual spin-valve, magnetic recording.

Micromagnetic simulations are performed to investigate the frequencies and relative amplitudes of resonant magnetic modes within nanomagnetic elements of varying size. It is found that the response of nanoscale magnetic elements with thickness of just a few nanometers to a pulsed magnetic field is dominated by two modes localized in the edge and in the center of the element.

Dual IrMn-pinnned current-perpendicular-to-plane giant magnetoresistive sensors for magnetic recording heads were investigated and their noise characteristics were compared to similar standard single sensors, using test structures with sizes down to 50 nm. The results of the comparison revealed that the intrinsic signal DELTA RA in the dual spin valves (SVs) increased by a factor of about 2 compared to the single SV, while the extra parasitic resistance of the second IrMn-pinned layer limited the DELTA R/R increase to a factor of about 1.5.

The magnetoresistance of antiparallel (AP) coupled self-pinned spin valves was measured utilizing Ir as a coupling layer. The magnetoresistance ratio increased quasilinearly from 2.2% to 4.0% with a reference layer thickness as expected from the Valet-Fert model in the long spin diffusion length limit.

The ferromagnetic resonance (FMR) in the Co(sub 80)Fe(sub 20)/Ni(sub 80)Fe(sub 20) free layer of micron-sized, magnetic tunnel junction (MTJ) devices is evaluated by two different techniques. The nonuniformities of the free layer magnetization and excitation of higher order standing spin wave modes explains the multiple resonance peaks observed by both complex impedance and mag-noise measurements.

Research into the manufacture and properties of thin AIN-based barriers for use in low resistance magnetic tunnel junctions is presented. It was possible to optimize the reactive sputter deposition of AIN at 20% nitrogen content in the sputter gas to produce stoichiometric, crystalline AIN with high quality interfaces in bottom PtMn tunnel-valve structures.

Research into the use of ultrathin Al2O3 barriers to produce low-resistance tunnel-valve sensors suitable for recording heads is presented. It was found that the production of bottom-antiferromagnet tunnel valves with ultrathin barriers and low junction resistances needs the use of a gentle oxidation technique to avoid a raised resistance because of pinned layer oxidation.

A study was conducted to analyze the preparation of exchange-biased spin valves supporting CoFeB amorphous layers. The samples were made in a magnetron sputtering system with a base pressure of 1x10(super -8) Torr and argon plasma pressure of 2 mTorr. The films were then deposited onto oxidized silicon substrates. Moreover, the hysteresis loops were determined in a superconducting quantum interference device magnetometer.

A study was conducted to analyze the Cl2-based plasma chemistry with the CO/NH3 mixture. Experimental results indicated that CO/NH3 plasma chemistry generates metal carbonyl etch products desorbed in the simultaneous presence of an ion flux. Findings also showed that the chemistry is very promising for shallow, corrosive-free etching of NiFe and NiFeCo. However, Cl2-based chemistries produce high rates because of a stronger chemical component.

Low-field magnetoresistance detection is performed by developing a new epitaxial spin value-type system which consists of Fe/Pd epitaxial multilayers grown on (100)MgO by molecular beam epitaxy. A sudden transition from positive to negative magnetization occurs when the hysteresis measurements are performed in reverse magnetic fields. The epitaxial spin value structures are constructed by the epitaxial growth of Fe/Ag, Co/Ag and Co/Cu bilayers.

Face-centered cubic (111)- and (001)-oriented Co(x)Pd(1-x) alloy thin films are grown by molecular beam epitaxy. The growth is performed on (111)Si and (001)MgO substrates, and the alloy films are 200 to 1000 angstroms thick. The films exhibit a perpendicular easy axis which indicates the presence of strong magnetic anisotropy which suppresses the demagnetizing field.

The precessional dynamics of a 2*2 [micro][m.sup.2] CoFe/NiFe element stimulated by an in-plane pulse magnetic field are examined by using time- and vector-resolved Kerr microscopy measurements and micromagnetic simulations. The simulations have shown that only the magnetization of the center region has undergone large angle reorientation, while the canted magnetization at the edges of the element has remained pinned.

The magnetotransport properties of current perpendicular to the plane giant magnetoresistive spin valves are examined by using [([[Co.sub.x][Fe.sub.100-x]).sub.100-y][Al.sub.y] . The spin-torque measurements have shown that the spin-torque current threshold is lower in CoFeAl spin valves than in standard CoFe spin valves.

Time-resolved scanning Kerr microscopy is used to study the response of square Ni88Fe12/Co80Fe20 bilayer elements to a pulsed magnetic field. Measurements are performed upon a square element of 600 nm size and upon 64, 120, 220, 425, and 630 nm square elements that formed square arrays of about 4000 nm total size.

Properties of magnetic tunnel junctions with aluminum oxide barriers alloyed with boron are described. Therefore, the microstructure of the metal film used to form the Al2O3-based amorphous oxide barrier does not appear to play a significant role in the integrity and low-resistance behavior of the resulting tunnel-valve sensor.