Competition of spin-flip and spin-flop dominated processes in magnetic multilayers: Magnetization reversal, magnetotransport, and domain structure in the NiFe/Cu system

Changes in the magnetization structure of an antiferromagnetically (afm)-coupled metallic multilayer as a function of the applied field H along the easy axis may involve both spin-flip and spin-flop events. The latter are widely discussed as the origin of the characteristic shapes of the magnetization M(H) and giant magnetoresistance (GMR) curves. In this work, we demonstrate the influence of spin-flip processes, which result in very different magnetization reversal and resistivity characteristics as compared to the spin-flop case: sharp, steplike GMR and magnetization changes for both the surface and internal layers-including magnetic viscosity effects-are observed. By means of Kerr microscopy, Kerr magnetometry, GMR, and magnetization measurements we show that spin-flip transitions via domain wall displacement constitute the relevant mechanism of magnetization reversal, provided that the anisotropy field H-K in the multilayer surpasses the antiferromagnetic coupling field H-afm. In this case, a linear dependence of the GMR on the magnetization is observed, whereas for fields applied along the hard axis magnetization rotation results in a quadratic dependence. The strong change of the ratio H-K/H-afm could be realized for measuring temperatures between 4.2 and 470 K in a series of wedge-type NiFe/Cu multilayers prepared by dc magnetron sputtering and showing GMR amplitudes of up to 12% (300 K) and 28% (4.2 K) in the second afm coupling maximum with extremely low values of the afm coupling strength

Full spin switch effect for the superconducting current in a superconductor/ferromagnet thin film heterostructure

Superconductor/ferromagnet (S/F) proximity effect theory predicts that the superconducting critical temperature of the F1/F2/S or F1/S/F2 trilayers for the parallel orientation of the F1 and F2 magnetizations is smaller than for the antiparallel one. This suggests a possibility of a controlled switching between the superconducting and normal states in the S layer. Here, using the spin switch design F1/F2/S theoretically proposed by Oh et al. [Appl. Phys. Lett. 71, 2376 (1997)], that comprises a ferromagnetic bilayer separated by a non-magnetic metallic spacer layer as a ferromagnetic component, and an ordinary superconductor as the second interface component, we have successfully realized a full spin switch effect for the superconducting current.Comment: 5 pages, 4 figure

Observation of the "Inverse" spin valve effect in a Ni/V/Ni trilayer system

An experimental study of magnetic and superconducting properties of a trilayer Ni/V/Ni thin film system grown on single-crystalline MgO(001) substrate is reported. The field dependence of the superconducting transition temperature T c for samples comprising Ni layers with similar values of the coercive field H c reveals no anomalies. However, in samples with different thicknesses of the nickel layers the difference in H c amounts up to ΔH c ~ 1.8 kOe, thus enabling to manipulate the relative orientations of the layers' magnetization by an external magnetic field. Surprisingly, for these samples the T c for the parallel orientation of the magnetizations of the Ni layers is higher, in a certain magnetic field range, than for the antiparallel one, at odds with theoretical predictions. Possible reasons of this contradiction are discussed. © Pleiades Publishing, Ltd., 2009

Unravelling the role of the interface for spin injection into organic semiconductors

Whereas spintronics brings the spin degree of freedom to electronic devices, molecular/organic electronics adds the opportunity to play with the chemical versatility. Here we show how, as a contender to commonly used inorganic materials, organic/molecular based spintronics devices can exhibit very large magnetoresistance and lead to tailored spin polarizations. We report on giant tunnel magnetoresistance of up to 300% in a (La,Sr)MnO3/Alq3/Co nanometer size magnetic tunnel junction. Moreover, we propose a spin dependent transport model giving a new understanding of spin injection into organic materials/molecules. Our findings bring a new insight on how one could tune spin injection by molecular engineering and paves the way to chemical tailoring of the properties of spintronics devices.Comment: Original version. Revised version to appear in Nature Physics

Depth Profiling Photoelectron-Spectroscopic Study of an Organic Spin Valve with a Plasma-Modified Pentacene Spacer

[[abstract]]We report an enhanced magnetoresistance (MR) in an organic spin valve with an oxygen plasma-treated pentacene (PC) spacer. The spin valve containing PC without the treatment shows no MR effect, whereas those with moderately plasma-treated PC exhibit MR ratios up to 1.64% at room temperature. X-ray photoelectron spectroscopy with depth profiling is utilized to characterize the interfacial electronic properties of the plasma-treated PC spacer which shows the formation of a derivative oxide layer. The results suggest an alternative approach to improve the interface quality and in turn to enhance the MR performance in organic spin valves.[[incitationindex]]SCI[[booktype]]電子

Hochstabile elektrische Funktionsschichten für miniaturisierte Chipbauelemente : IFW-Teilbericht für das Verbundvorhaben: Neue Keramik- und Dünnschichtwerkstoffe für miniaturisierte Chipbauelemente

[no abstract available

Degradation of NiCr/CuNiMn/NiCr films on alumina substrates

Bruckner W, Edelmann J, Vinzelberg H, Reiss G, Knuth T. Degradation of NiCr/CuNiMn/NiCr films on alumina substrates. Thin Solid Films. 1996;280(1-2):227-232.This paper addresses the aging behaviour of NiCr/CuNiMn/NiCr triple layers on Al2O3 ceramics at temperatures up to 200 degrees C for film thicknesses d greater than or equal to 0.5 mu m. Investigations of the film structure and the increase of resistance and its temperature coefficient during the annealing process and studies of the dependence of this aging drift on both the film thickness and the storage temperature have been carried out. Furthermore, the film stress and the effect of substrate bending on resistance have been measured. The results can be explained by the irregular film structure (columns and small bridges between them), which causes stress and current concentrations as well as local creeping, cracking and oxidation processes in the micro-bridges. They are compared with such for structurally homogeneous films on silicon wafers