D. S. Lashmore

Giant magnetoresistance peaks in CoNiCu/Cu multilayers grown by electrodeposition

Giant magnetoresistance (GMR) of CoNiCu/Cu multilayers grown by electrodeposition was measured as a function of the copper layer thickness and effects of the order of 14% were obtained. The copper layer thickness ranged from 0.7 to 3.5 nm. Two peaks in the magnetoresistance were observed. One was centered at a copper thickness of ∼1.0 nm and the second was centered at ∼2.3 nm. Comparison of the field dependence of the magnetoresistance with the field dependence of the magnetization, as determined by vibrating‐sample magnetometer, suggests that the saturation field for GMR and the magnetization are similar for the larger copper thicknesses, but are strikingly different near 1.0 nm copper thickness. This observation suggests that the GMR is affected by different factors depending on the thickness of the copper layer.

Giant magnetoresistance in electrodeposited Co–Ni–Cu/Cu superlattices

We have electrodeposited a series of Co–Ni–Cu/Cu superlattices in which the Cu layer thickness was varied between 7 and 35 A and the Co–Ni–Cu alloy layer thickness held constant. ‘‘Giant magnetoresistance’’ was observed for all films, with the magnitude of the effect decreasing with increasing Cu spacer layer thickness.

Growth and characterization of electrodeposited Cu/Cu-Ni-Co alloy superlattices

Abstract We have used a recently developed potentiostatic technique to electrodeposit Cu/Cu-Ni-Co alloy superlattices from a single electrolyte. Our films have been characterized using X-ray diffraction, electron backscatter diffraction patterns and electron probe microanalysis. Good epitaxy and repeat distances as short as 15 A have been achieved.

Properties of electrodeposited Co‐Cu multilayer structures

Alternate layers of Co and Cu of individual layer thicknesses from 1.5 to 8.0 nm and total thickness of about 100 layers and of Co bilayers separated by Cu have been electroplated from an electrolyte having a low concentration of Cu and a high concentration of Co atoms. The properties of the resulting structures have been analyzed using SEM, x‐ray diffraction, VSM, and FMR methods. Comparable structures have also been fabricated by e‐beam evaporation in high vacuum for comparison purposes. X‐ray diffraction patterns indicate only the fcc structure. Assuming the Co thickness to be that deduced from the plating charge, we infer 4πM values in the range 6.0–14.5 kG from VSM and FMR. Some uniaxial anisotropy is apparent in this system. These results are similar to those of earlier work on thin fcc Co layers in the same range of thicknesses, where the room‐temperature moment was reduced but depended only slightly on layer thickness, and where the uniaxial anisotropy was observed to be small.

Magneto‐optical indicator film observation of domain structure in magnetic multilayers

A new method is developed using a transparent indicator ferrimagnetic magneto‐optic film with in‐plane anisotropy for visualization and direct experimental study of dynamic magnetization processes and nondestructive characterization of the defect structure of magnetic multilayers. Some examples of its application to the investigation of peculiarities of the as‐grown magnetic structure of electrochemically produced CoNiCu/Cu multilayers with a giant magnetoresistance (GMR) effect and magnetization reversal by domain wall motion are described.

Magnetic properties of electrodeposited copper-nickel composition-modulated alloys

Abstract Pulsed potentiostatic deposition offers a new technology for the production and stabilization of composition-modulated alloy (CMA) structures. Using this new technology, a series of Cu-Ni-modulated structures with layer thickness in the to 6 nm range were prepared. The first transmission electron micrographs of electrodeposited CMA are presented, showing the existence of sharp interfaces. Magnetic properties of the CMA structures were measured by vibrating sample and SQUID magnetometers, and by ferromagnetic resonance.

Fourfold anisotropy of an electrodeposited Co/Cu compositionally modulated alloy

Abstract A compositionally modulated alloy of 3 nm layers each of Cu and Co was electrodeposited on a (100) oriented Cu single crystal substrate. Anisotropy with fourfold symmetry in the plane of the film was investigated using ferromagnetic resonance, vector VSM techniques, and measurements of magnetic viscosity. This anisotropy is thought to be the first such effect to be observed in multilayered samples produced by either sputtering or electrodeposition. The anisotropy energy, K 1 , is roughly consistent with values published for fcc cobalt.

Magnetization and magnetic aftereffect in textured Ni/Cu compositionally-modulated alloys

Abstract The magnetic properties of Ni/Cu compositionally-modulated alloys with [100], [110] and [111] textures were measured by magnetometry and ferromagnetic resonance. These alloys were found to exhibit a pronounced magnetic aftereffect.

Giant magnetoresistance of electrodeposited CoNiCu/Cu multilayers

Abstract Giant magnetoresistance (GMR) has been studied in electrodeposited CoNiCu/Cu multilayers. The value of the change of resistance with field, ΔR, is almost constant when the temperature is lowered to 15 K, whereas the GMR = ΔR R is, of course, increased. The magnetic field dependence is unchanged with temperature, demonstrating that the GMR is not thermally activated. Lorentz electron microscopy was used to investigate the nature of the magnetic domains. The layers are antiferromagnetically coupled, and the domains extend without interruption for ≈ 200 nm along the layers.

Dynamics of domain structure in magnetic multilayers

We use a new method for visualization and direct experimental study of dynamic magnetization processes and for nondestructive characterization of the defect structure of magnetic multilayers. The method utilizes a transparent indicator ferrimagnetic magneto-optic film with in-plane anisotropy. An example of its application to the investigation of the magnetization reversal by domain wall motion in electrochemically produced CoNiCu/Cu multilayers which exhibit a giant magnetoresistance effect is described.