INFLUENCE OF fd INTERACTION ON TUNNEL MAGNETORESISTANCE AND MAGNETOIMPEDANCE IN ISLAND Fe / Gd2O3 NANOSTRUCTURES

A.Kasumov*,
      

I. M. Frantsevich Institute for Problems of Materials Science of the NAS of Ukraine, Omeliana Pritsaka str.,3, Kyiv, 03142, Ukraine
kasumov@ipms.kiev.ua
Powder Metallurgy - Kiev: Frantsevich Institute for Problems of Materials Science NASU, 2024, #01/02
http://www.materials.kiev.ua/article/3679

Abstract

The potential for amplifying tunnel magnetoresistance and magnetoimpedance in island nanofilms without energy consumption or the use of amplifying devices was studied. Such amplification was observed for the films deposited on a Gd2O3 layer instead of a glass substrate. The enhancement is due to the fd exchange interaction established between atoms with unfilled f- and d-electron shells, present in both Fe and Gd2O3. The fd exchange interaction enhances the ordering of the magnetic structure within the Fe ferromagnetic layer, increases its magnetization, and subsequently improves the properties that depend on this magnetization. Iron and Gd2O3 were selected because the magnetic moments of Fe in the iron group and Gd in the lanthanide series are among the highest effective ones: μFe = 7.13 μB  and μGd = 7.95 μB. This, according to theory, determines the high energy of the fd exchange interaction. The island morphology of Fe films deposited on a Gd2O3 layer enabled electron tunneling under the influence of the fd exchange interaction. This allowed the study of tunnel magnetoresistance under direct current and magnetoimpedance under alternating current influenced by the fd exchange interaction. The frequency dependence of the active component Ζ', the reactive component Ζ'', and the total impedance Ζ of Fe films on glass and Gd2O3 substrates, without and under a constant magnetic field of 7500 Oe, was analyzed. These characteristics are used to determine the frequency dependence of tunnel magnetoimpedance and estimate tunnel magnetoresistance for Fe island films on glass and Gd2O3 substrates. These characteristics were found to be 55% higher, on average, for Fe deposited on Gd2O3 than for Fe on glass, both at a low frequency of 0.1 Hz for tunnel magnetoresistance and at higher frequencies of 1–105 Hz for tunnel magnetoimpedance. This results from the influence of fd exchange interaction on electron tunneling between the iron islands


FE, F–D EXCHANGE INTERACTION, GD2O3, ISLAND FILMS, TUNNEL MAGNETORESISTANCE, TUNNELING MAGNETOIMPEDANCE