Magnetic tunnel junctions with impurities

TL;DR

This paper theoretically investigates how impurities within the insulating barrier of magnetic tunnel junctions affect the current and tunnel magnetoresistance, revealing conditions for significant enhancement and diode-like behavior.

Contribution

It introduces a theoretical model showing impurity effects on I-V characteristics and TMR, highlighting the impact of impurity energy levels and position.

Findings

Impurities near the Fermi energy greatly enhance current and TMR.

Asymmetric impurity placement induces diode-like I-V behavior.

Impurity energy alignment is crucial for tunneling properties.

Abstract

The influence of impurities, embedded into the isolating spacer (I) between two ferromagnetic electrodes (F), on the I-V curve and tunnel magnetoresistance (TMR), is theoretically investigated. It is shown, that the current and TMR are strongly enhanced in the vicinity of the impurity under the condition that the energy of the electron's bound state on the impurity is close to the Fermi energy. If the position of the impurity inside the barrier is asymmetric, e.g. closer to the one of the interfaces F/I the I-V curve exhibits quasidiode behavior.