Model features of films of iron nanoislands that determine electron tunneling

DOI: 10.62564/M4-KK1323

Kostyantyn Korotkov, Alexander Dmitriev, Anatoliy Kasumov, Arsenii Ievtushenko

Frantsevich Institute for Problems of Materials Science National Academy of Science of Ukraine


Iron island films with a thickness of less than 30 nm undergo rapid surface oxidation in air, which significantly changes their conductivity-related properties, such as the inter-island electron tunneling[1]. The purpose of this work is to study this process. The study of the temperature dependence of the resistivity of oxidized iron films has shown that when the film thickness decreases below 35 nm, a transition from a metallic conduction mechanism with a characteristic linear shape to an activation (exponential) shape occurs. The activation process in this case may consist of electron tunneling between Fe islands. This means that a film thickness of 35 nm is critical [2] for initiating the process of percolation of the islands. The activation energy of oxidized Fe films is 0.018 eV, which is close to the value of 0.01 - 0.001 eV obtained for unoxidized films. In other words, the activation energy depends mainly on the size of the islands and the distance between them, rather than on their chemical composition. The arrangement of oxidized iron island films on rare earth metal (RΕΜ) oxide leads to a d-f exchange interaction between d-atoms of iron and f-atoms of REΜ. This interaction organizes the magnetic structure of Fe and magnetite, i.e., increases the orientation of electron spins in them [3]. The study showed that the resistivity of oxidized Fe films on REM oxide is lower than on glass due to the higher order of spins in the islands and the absence of energy consumption for spin transfer during electron tunneling between them. In this regard, the tunneling magnetoresistance (TMR) in oxidized Fe films has a negative sign, and when the film is on REM oxide, the TMR value is higher than when it is on substrates made of other materials. Thus, the model of island films allows us to understand the peculiarities of their conductivity under different experimental conditions.

Keywords
d-f exchange interection, TMR, modeling

Acknowledgments
Not provided

References
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