GMR Effect In Sputtered Permalloy/Cu Multilayers.

Abstract

The GMR effect of the [(Ni₈₃Fe₁₇=Py)/Cu]x100 multilayers (Mls) obtained by d. c. face-to-face sputtering technique deposited onto Si wafers were studied at room temperature (R. T.) and at 4.2 K. The GMR(d_Cu) oscillatory behaviour as well as the width of the first and the second AF coupling ranges have been found to be strongly affected not only by the presence of the superparamagnetic entities located at the Py/Cu interfaces but mainly by the existence of the magnetic bridges between Py sublayers. Zero-field-cooled and field-cooled magnetisation measurements confirmed the existence of the paramagnetic/superparamagnetic areas (at R. T.) for Py thicknesses up to 2.5 nm. The effectiveness of the magnetic bridges between Py sublayers has been found to be temperature dependent, leading to the temperature dependence of the remnant to saturation magnetisation ratio.