Tunneling magnetoresistance with sign inversion in junctions based on iron oxide nanocrystal superlattices.

Lekshmi, Indira Chaitanya; Buonsanti, Raffaella; Nobile, Concetta; Rinaldi, Ross; Cozzoli, Pantaleo Davide; Maruccio, Giuseppe · ACS Nano · 2011

basic_science · Level V

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Abstract

Magnetic tunnel junctions sandwiching a superlattice thin film of iron oxide nanocrystals (NCs) have been investigated. The transport was found to be controlled by Coulomb blockade and single-electron tunneling, already at room temperature. A good correlation was identified to hold between the tunnel magnetoresistance (TMR), the expected magnetic properties of the NC arrays, the charging energies evaluated from current-voltage curves, and the temperature dependence of the junction resistance. Notably, for the first time, a switching from negative to positive TMR was observed across the Verwey transition, with a strong enhancement of TMR at low temperatures.

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