Giant Magnetoresistance Multilayers Research Articles

Giant magnetoresistance in heterogeneous alloy films

Giant magnetoresistance (GMR) in heterogeneous alloy films offers an alternative to GMR in multilayers and spin valves in a potentially simpler structure. In this review, the general features or GMR in these heterogeneous films are discussed. These include film preparation, structure, magnetic properties and magnetoresistive behavior and the possible correlations among these features. It is emphasized that we are at a very early stage in the development of this subject. In particular, much more detailed microstructural data are required in order to formulate a reliable model. >

High frequency permeability measurements on Ni/sub 76/Fe/sub 10/Co/sub 14//Cu giant magnetoresistive multilayers

High frequency permeability was measured on a [Ni/sub 76/Fe/sub 10/Co/sub 14/(16 /spl Aring/)/Cu(23 /spl Aring/)]/sub 10/ giant magnetoresistive multilayer. The real part of the permeability was essentially flat at least up to 100 MHz with a value of 360. The intrinsic anisotropy field, and the bilinear and the biquadratic exchange fields were determined from measurements of the transverse biased permeability along both the easy and hard axes. >

GMR materials for low field applications

The higher magnetoresistance of giant magnetoresistance (GMR) material offers potential improvements for magnetoresistive random access memory (MRAM), magnetoresistive read heads, and magnetic field sensors. Saturation field, linearity, hysteresis, sheet resistivity, magnetostriction, and other factors can impact the utility of GMR materials in applications. These factors are compared for several GMR structures: magnetic sandwiches and multilayers, antiferromagnetic-coupled and uncoupled sandwiches and multilayers, vertical GMR multilayers, and granular films. The most promising GMR materials for low field applications are uncoupled sandwiches and low antiferromagnetic coupled multilayers using inplane conduction. They can be superior to anisotropic magnetoresistance (AMR) materials and Hall effect devices for many applications.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Theory of the conductivity and giant magnetoresistance in magnetic multilayers.

A simple, analytic expression is derived for the conductivity of thin films with the use of the coherent-potential approximation. With the use of our conductivity formula, the giant magnetoresistance in multilayers consisting of magnetic and nonmagnetic layers, is discussed based on a numerical calculation for seven-layer Fe/Cr films and a phenomenological analysis for a simple model.

Preparation of Giant Magneto-Resistive Multilayers for Dual Truck Complementary Thin Film Heads

Dual truck complementary head has been proposed in this study. It was confirmed that the recording mechanism was correct in principle through the read-write charactristics using conventional thin film head. Thin film with giant magneto-resistivity GMR ratio is required to construct the hybrid type of read-write head. Ni-Fe/Cu multilayers with Cu layer thickness of 10A prepared by ion beam sputtering method exhibited high magneto-resistivity (MR) ratio as large as aobut 16%. The multilayer seemed to be suitable for detecting of flux reversal in dual truck complementary heads.

Sputter deposition of giant magnetoresistive Co-Cu multilayers

We have used UHV dc magnetron sputtering to deposit giant magnetoressive Co-Cu multilayers on Si substrates. The largest magnetoresistances are obtained in films which are deposited using the lowest sputtering pressures, and which therefore experience the most energetic bombardment during deposition. The large magnetoresistances are caused not by comparatively small resistivities in an applied magnetic field, but by relatively large zero-field resistivities. Structural features associated with low sputtering pressures allow substantial antiferromagnetic alignment of Co layers in zero field. The smaller the sputtering pressure, the greater the antiferromagnetic alignment, the greater the zero-field resistivity and the further the sample resistivity is able to fall when a magnetic field changes the alignment from antiferromagnetic to ferromagnetic. Multilayers of Co-Cu made by evaporation may not show substantial magnetoresistance because, unlike sputtering, evaporation transfers little energy to the instantaneous surface of a growing film.

Giant magnetoresistance dependence on Ar acceleration voltage in Co9Fe/Cu and Co3Fe/Cu multilayers

In relation to theoretical predictions on the importance of randomness at the interface to determine the cause for giant magnetoresistance, argon acceleration voltage (VB) in ion beam sputtering was changed for preparing a set of CoxFe1−x/Cu multilayers. We found that the magnetoresistance as quite sensitive to the argon acceleration voltage and had a maximum around VB=600 V. Perfect antiferromagnetic coupling of the CoxFe1−x layers via thin Cu layers and the oscillation behavior of this indirect exchange coupling with a 12 Å period were observed for VB=600 V. These results suggest the importance of the interface state for giant magnetoresistance in multilayers. We also found that a small saturation field can be induced, which can be explained by the metamagnetic transition associating the relation of Ku≳J/tCoFe.

The role of spin-dependent impurity scattering in Fe/Cr giant magnetoresistance multilayers

To probe the mechanism of giant magnetoresistance (GMR) observed in Fe/Cr multilayers, we have sputter deposited at the interfaces of Fe(15 Å)/Cr(12 Å) multilayers an additional, ultrathin (0–4 Å) layer of a variety of third elements (V, Mn, Ge, Ir, and Al). When alloyed with Fe in dilute concentrations, the elements chosen have known resistivities for spin-up (ρ↑) and spin-down (ρ↓) currents arising from spin-dependent impurity scattering. The results show a clear correlation between α=ρ↓/ρ↑ of the respective element and the way in which GMR varies with the ultrathin layer thickness. In addition, little difference in GMR is observed between multilayers where the ultrathin layer thickness t/2 is deposited on every Fe/Cr interface and those with a thickness t deposited on alternate interfaces. This investigation demonstrates the importance of the type and total number of scattering centers per multilayer period to the GMR effect.