Interface intermixing and magnetoresistance in Co/Cu spin valves with uncoupled Co layers

The interpretation of experiments on the effect of interface intermixing on the giant magnetoresistance (GMR) effect in antiferromagnetic-coupled multilayers can be complicated by the fact that interface intermixing also changes the coupling strength; therefore, we have grown an artificially intermixed region in Co/Cu spin valves with uncoupled Co layers. The structure we used was a newly engineered spin valve composed of 100 Å Co+6 Å Ru+25 Å Co+40 Å Cu+100 Å Co. Here the Ru layer provides an antiparallel alignment of the Co layers and the Cu layer decouples the upper two Co layers. An intermixed CoCu region has been grown at the Cu/Co interface and in some cases also at the Co/Cu interface by alternately sputtering 1 Å Co and 1 Å Cu. X-ray measurements confirm the existence of an intermixed region, although no reduction of magnetic moment is observed as is reported for homogeneous sputtered Co0.5Cu0.5 alloys. This indicates the existence of Co clusters in the intermixed regions. There is no difference in GMR between an intermixed layer of thickness t at one Co/Cu interface or two intermixed layers of thickness t/2 at both Co/Cu interfaces. Thus, it seems that the total thickness of the intermixed regions is decisive for the magnitude of the GMR. Because G, ¿G, and ¿G/Gap all show a gradual decrease when the nominal thickness of the intermixed region increases from 0 to 36 Å, this indicates that there is no strong spin-dependent scattering in this region. This is in agreement with calculations on a model bilayer Co/Cu/Co with the Camley–Barnas model

In-plane and out-of-plane anisotropic magnetoresistance in Ni80Fe20 thin films

The anisotropic magnetoresistance (AMR) has been measured for Ni80Fe20 thin films, with the magnetization vector rotating in the film plane as well as out of the film plane. The out-of-plane (OF) AMR is found to be considerably larger than the in-plane (IF) effect, and strongly dependent on the degree of texture. In untextured films, the difference between the IP- and the OP-AMR is explained in terms of a dimensionality effect, whereas in (111)-textured films an additional contribution to the OP-AMR is found

On the ferromagnetic interlayer coupling in exchange-biased spin-valve multilayers

The ferromagnetic interlayer coupling in sputter-deposited permalloy/copper/permalloy exchange-biased spin valve multilayers has been measured as a function of the copper thickness. The variation with thickness may, for tcu>1.7 nm, be analyzed in terms of the Neel model for magnetostatic coupling due to correlated interface roughness, using parameters which are consistent with the observed microstructur

Semiclassical calculations of the anisotropic magnetoresistance of NiFe-based thin films, wires, and multilayers

The anisotropic magnetoresistance (AMR) at low temperatures is theoretically studied for low-dimensional NiFe-based systems in various geometries by solving the Boltzmann transport equation. The AMR is treated by introducing spin-dependent anisotropic mean free paths, making use of anisotropic-scattering parameters that are extracted from experimental spin-resolved resistivity data for bulk dilute NiFe alloys. A first set of calculations comprises the AMR in NiFe thin films and cylindrical wires, as a function of the layer thickness and wire diameter, respectively. For the thin film case we have considered rotation of the magnetization vector within the film plane as well as out of the film plane. For the latter the highest AMR ratio is found, which even slightly exceeds the bulk value. For wires the dependence of the AMR on the dimensions is qualitatively different as compared to the film case due to the relatively enhanced importance of boundary scattering. Finally, the validity of a description of the combined effect of AMR and the giant magnetoresistance in terms of a simple summation of the two effects is studied by performing model calculations for NiFe/Cu/NiFe trilayers

Grain Size and Strain in Sputter Deposited Ni0.8Fe0.2 and Cu Films

The average grain size and strain in the direction parallel to the surface of thin Ni0.8Fe0.2 and Cu films, sandwiched between Ta layers, have been determined as a function of layer thickness by grazing incidence X-ray diffraction. The in-plane grain size and grain size distribution were also assessed by plan-view transmission electron microscopy. Standard ¿-2¿ X-ray powder diffraction was used to determine the uniform strain in the direction perpendicular to the surface. Both for Ni0.8Fe0.2 and Cu, an elongation of the lattice parameter perpendicular to the surface and a compression of the lattice parameter in the plane of the film is observed, which decreases with increasing film thickness. Additionally, for Ni0.8Fe0.2 a non-uniform elongation of the perpendicular interactomic distance at the Ta interfaces is deduced by fitting a kinematical model to the ¿-2¿ diffraction spectrum. This study illustrates the strength and the complementary character of standard powder X-ray diffraction, grazing incidence X-ray diffraction and transmission electron microscopy for the structural analysis of thin metal films

Grain Size and Strain in Sputter Deposited Ni0.8Fe0.2 and Cu Films

The average grain size and strain in the direction parallel to the surface of thin Ni0.8Fe0.2 and Cu films, sandwiched between Ta layers, have been determined as a function of layer thickness by grazing incidence X-ray diffraction. The in-plane grain size and grain size distribution were also assessed by plan-view transmission electron microscopy. Standard ¿-2¿ X-ray powder diffraction was used to determine the uniform strain in the direction perpendicular to the surface. Both for Ni0.8Fe0.2 and Cu, an elongation of the lattice parameter perpendicular to the surface and a compression of the lattice parameter in the plane of the film is observed, which decreases with increasing film thickness. Additionally, for Ni0.8Fe0.2 a non-uniform elongation of the perpendicular interactomic distance at the Ta interfaces is deduced by fitting a kinematical model to the ¿-2¿ diffraction spectrum. This study illustrates the strength and the complementary character of standard powder X-ray diffraction, grazing incidence X-ray diffraction and transmission electron microscopy for the structural analysis of thin metal films

Characterization and modeling of atomic layer deposited high-density trench capacitors in silicon

A detailed electrical analysis of multiple layer trench capacitors fabricated in silicon with atomic-layer-deposited Al2O3 and TiN is presented. It is shown that in situ ozone annealing of the Al2O3 layers prior to the TiN electrode deposition significantly improves the electric properties of the devices such as the dielectric constant, leakage current, and the breakdown voltage of the devices. The self-inductance and self-resistance of the capacitors as derived from S-parameter measurements up to 10 GHz are very small, as low as 4 pH and 6 mO for 19.1 mm2 electrode surface. These data are shown to be consistent with a theoretical model