1/f noise in patterned GMR spin valves

abstract onl

Magnetization reversal of NiFe films exchange-biased by IrMn and FeMn

We have used the transmission electron microscope to study how the magnetization reversal mechanism of thin NiFe layers exchange-biased by IrMn and FeMn varies over a wide temperature range, The reversal behaviour was qualitatively similar for layers biased by both types of antiferromagnet, At room temperature and below the most striking feature was the scale of the domain structures observed. Very high density domain structures with micron (or sub-micron) wall separations developed. By contrast at elevated temperatures, the reversal mechanism simplified. This is consistent with there being a strong local variation of the pinning strength between the NiFe and the antiferromagnetic layer, The overall temperature variation of the pinning changes much more rapidly than the magnetic properties of an isolated NiFe layer over a similar temperature range

Pulsed laser deposition of permanent magnetic Nd2Fe14B thin films

Pulsed Laser Deposition (PLD) is applied to deposit thin (thickness typically 100 nm) films of Nd2Fe14B. It is shown that films can be grown which have the desired composition and phase. Nd2Fe14B grows with the c-axis along the film normal on 110 Al2O3 single crystal substrates covered with a Ta layer. These films are found to have a strong magnetic anisotropy along this axis

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

Enhanced anisotropy of permalloy layers sputter deposited on V-grooved substrates and tilted surfaces

The magnetic anisotropy of 8–100 nm thick Ni80Fe20 films sputter deposited on nanostructured V-grooved substrates and on tilted surfaces is investigated. Films deposited on a V-grooved substrate (200 nm period) with the sidefaces at an angle of 55° to the substrate plane, show a very large and essentially thickness-independent magnetic anisotropy field, viz. 25±3 kA/m. Planar reference films deposited also at an angle of 55° to their substrate normal show an increase of the magnetic anisotropy as well, but only to 8 kA/m, independent of the film thickness, which is explained as a growth-induced effect. It is argued that the enhanced anisotropy observed in the V-grooved substrates is not the result of shape anisotropy induced by the V-grooves. This leads to the conclusion that the observed enhanced anisotropy must also be a growth-induced effect, enhanced by the specific geometry of the V-grooves

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