Giant Magnetoresistance Behavior Research Articles

Effect of Annealing on Interface Structure and Giant Magnetoresistance Oscillation in Co/Cu Multilayers

The effect of annealing on the oscillatory behavior of giant magnetoresistance (GMR) is studied in Co/Cu multilayers. Annealing at 200° C in vacuum reduces the height of the 1st peak of GMR oscillation significantly. However, the degradation of interface measured by X-ray diffraction is not large compared with the change in GMR. Microscopic change of the interface state causes ferromagnetic interlayer coupling between adjacent Co layers and diminishes the 1st GMR peak. The 2nd GMR peak, on the other hand, is not so sensitive to the degradation of the interface.

TEM studies in melt-spun Cu-Mn-Al system exhibiting giant magnetoresistance

Giant magnetoresistance (GMR) has recently been observed in a new system, melt-spun ribbons of Cu-Mn-Al, with /spl Delta/R/R(0)=15% at 30 K. The GMR behavior in this system has been extensively studied for a range of compositions. It is suggested that the onset of GMR may be attributed to the appearance of tweed microstructure in the ferromagnetic Cu/sub 2/MnAl phase. It has also been observed that GMR existed in all samples consisting of a mixture of varying amounts of Cu/sub 2/MnAl and Cu/sub 9/Al/sub 4/ phases. Extensive transmission electron microscopy studies have been carried out to evaluate the microstructural evolution of the tweed and the observed phases, and to correlate the microstructure with the observed GMR behavior.

Giant magnetoresistance of melt-spun Cu-Ni-Fe alloys with spinodally-decomposed structure

We report the observation of giant magnetoresistance effect in as-spun and annealed spinodally decomposed Cu-Ni-Fe alloy ribbons. The magnetoresistance ratio of 9.5% was observed at 4.2 K for as-spun Cu/sub 70/Ni/sub 15/Fe/sub 15/ ribbon, which could be increased to 12.0% by annealing at 400 C for 15 min. In contrast to the temperature dependence of the magnetoresistance ratio of sputtered Cu-Ni-Fe films, melt-spun Cu-Ni-Fe ribbons show an increase in the magnetoresistance ratio upon cooling from room temperature to 4.2 K. The observed giant magnetoresistance behavior in Cu-Ni-Fe ribbons is mostly caused by the spin-dependent scattering at the two-phase interface and in the ferromagnetic phase, as well as scattering due to magnetic fluctuations such as very fine ferromagnetic particles.

Giant magnetoresistance in spinodally decomposed Cu–Ni–Fe films

We report the observation of the GMR effect in spinodally decomposed Cu–20Ni–20Fe thin films. A ΔR/R value as high as 6.5% was observed at room temperature. In contrast to the commonly observed temperature-dependent behavior of ΔR/R increasing at low temperature; thin film shows a decrease in ΔR/R at 4.2 K. The dependence of the GMR effect on various deposition parameters, such as substrate temperature has been studied. The observed giant magnetoresistance behavior in Cu–20Ni–20Fe films is most likely related to the field-induced decrease in electron scattering in a pseudosuperparamagnetic material, as well as the spin-dependent scattering at the two-phase interface and in the ferromagnetic phase.

Creation of bulk, superlatticelike structure and giant magnetoresistance effect in a deformed Cu-Ni-Fe alloy

A spinodally decomposed Cu-20 Ni-20 Fe alloy containing ∼500 Å size ferromagnetic particles was uniaxially deformed to create a locally multilayered, superlatticelike structure with alternating ferromagnetic and nonmagnetic layers. When the size scale of each layer was made to be small, ∼15 Å thick, a dramatic improvement in room-temperature magnetoresistance ratio from ∼0.6 to ∼5% was obtained. An abnormal temperature dependence of magnetoresistance ratio, i.e., the room-temperature value being greater than that at 4.2 K, was found. The observed giant magnetoresistance behavior could be explained in terms of the field-induced decrease in electron scattering in a nearly superparamagnetic material although the spin-dependent scattering at the two-phase interface and in the ferromagnetic phase may also be a contributing factor.