Articles you may be interested inInfluence of the domain structure of nano-oxide layers on the transport properties of specular spin valves Comparative study of magnetoresistance and magnetization in nano-oxide specular and nonspecular MnIr/CoFe/Cu/CoFe spin valves from 10 to 300 K

Synthetic spin valves with structure of sub/Ta/NiFe/IrMn/AP2/Ru/AP1/Cu/CoFe/Ta were systematically studied by varying the Ru thickness in the artificial antiferromagnetic structure. Spin-valve films were deposited using a Nordiko 9606 PVD system and annealed in a magnetic field of 6 kOe parallel to the easy axis of the free layer. MR(H) and M(H) curves of these spin valves were experimentally measured and quantitatively simulated using Boltzmann transport equation and coherent magnetization rotation model. The corresponding interlayer exchange coupling and pinning angle of these spin valves were determined from simulation. Both experimental measurement and simulation results have shown that the characteristics of synthetic spin valves depend strongly on the thickness of Ru. The pinning field for spin valves with ultrathin Ru layer was canted. This was evidenced in the reduction of the measured MR ratio and shape of MR curve when Ru is thinner than 0.5 nm. It is concluded that the pinning angle is determined by the spin–flop angle of one of the pinned layers (AP2) at spin–valve annealing temperature, which is in turn determined by the final balance between the interlayer antiferromagnetic coupling field and the external applied magnetic field during annealing.

The reduction of roughness, without introducing damage, of thin-film surfaces in giant magnetoresistance ͑GMR͒ applications will be essential in the development of advanced devices. Tools and methods to accomplish this are limited at present. Gas-cluster ion beam ͑GCIB͒ technology shows promise as a dry, low-temperature process that can provide substantial improvement, and can be integrated into GMR-film deposition-and-etch tools. In this work, we describe recent GCIB technique developments and processes for tantalum, alumina, permalloy, and other relevant materials. With argon GCIB it is possible to reduce the roughness of many films to well below a nanometer ͑root-mean-square͒, with the roughness falling exponentially with cluster dose. Prototype magnetic films for evaluation were fabricated on GCIB-smoothed alumina gap layers. Transmission electron microscopy revealed changes in roughness and grain morphology that may be correlated with magnetic properties.

A new spin-filter spin valve with nano-oxide specular layers with structure of Ta/NiFe/IrMn/CoFe/NOL1/CoFe/Cu/CoFetfl/CutCu/NOL2/Ta was deposited using a Nordiko 9606 physical vapor deposition system. The data clearly show that the magnetoresistive (MR) ratio has been significantly improved for spin valves with thinner free layers. The MR ratio remains larger than 12% even when the CoFe free layer is as thin as 1 nm. An optimized MR ratio of ∼15% was obtained when tfl was about 1.2 nm and tCu about 1.5 nm, and was a result of the balance between the increase in the electron mean free path difference and current shunting through the conducting layer. It is also found that the Cu enhancing layer can improve soft magnetic properties of the CoFe free layer due to the low atomic intermixing observed between Co and Cu. The CoFe free layer of 1–4 nm exhibited coercivity of ∼3 Oe after annealing in a static magnetic field. This kind of spin valve with a very thin soft CoFe free layer is particularly attractive for ultra high density read head applications.

This paper and its companion paper describe the comparison between a one-dimensional theoretical model of a hydrogen discharge in a magnetic multipole plasma source and experimental measurements of the plasma parameters. The discharge chamber, described here, has been designed to produce significant densities of H − ions by incorporating a weak transverse field through the discharge to obtain electron cooling so as to maximize H − production. Langmuir probes are used to monitor the plasma, determining the ion density, the electron density and temperature and the plasma potential. The negative density is measured by photo-detachment of the extra electron using an intense laser beam. The model, described in the companion paper, uses the presented source geometry to calculate these plasma quantities as a function of the major arc parameters; namely the arc current and voltage and gas pressure. Good agreement is obtained between theory and experiment as a function of position and arc parameters.