Interações magnéticas em tricamadas Co/Cr/NiFe analisadas por medidas de magnetização em função do campo magnético

Abstract

The present work deals an experimental analysis of the structural and magnetic properties of trilayers, which are thin films, formed by two ferromagnetic layers separated by a non-magnetic layer. One of the ferromagnetic layers is composed by cobalt, the other one, by a nickel-iron alloy, while the nonmagnetic layer, by chromium. The thicknesses of the films are of the order of

nanometers and these were produced onto single-crystalline wafers of silicon

by the magnetron sputtering technique, using high purity targets. By x-ray

reflectivity measurements, the layer thicknesses were verified. Two trilayer

systems were produced. In the first one, the thickness of the ferromagnetic

layers was fixed and the chromium thickness was varied. In the other one, the

cobalt thickness was varied; remaining fixed the thicknesses of the other layers.

Both systems were used in order to analyze the magnetic interactions between

two ferromagnetic layers, with different magneto-crystalline anisotropies, across

a non-magnetic layer. These analysis were performed by measurements of

magnetization as a function of the applied field from which, the anisotropy

energy and the exchange interaction

constants were obtained, by using a phenomenological model which considers such interactions. For the first system, it was observed that the exchange interaction constant oscillates between positive and negative values as a function of the chromium thickness. This is associated to a parallel and antiparallel alignment, respectively, of magnetizations. For the second system, a decrease of the exchange interaction constants with the cobalt thickness was observed and it can be attributed to a change of the crystalline anisotropy of cobalt.