Study of the Insulating Layer and Interfaces of MgO-Based Magnetic Tunnel Junctions by Impedance and Capacitance Spectra

Abstract

We have systematically investigated the complex impedance (CI) and complex capacitance (CC) spectra of MgO-based magnetic tunnel junctions (MTJs) due to successive annealing. The variation of the tunnel magnetoresistance (TMR) ratio due to annealing can be related to the change of interfacial trap states and textured MgO based on the analysis of CI spectra by an equivalent circuit model. The results of CC spectra are also consistent with the analysis of CI and observed TMR ratio variation. The CI and CC techniques are also powerful to characterize the oxide-based MTJs.Index Terms-Complex capacitance (CC), complex impedence (CI), MgO, equivalent circuit model (ECM), tunnel magnetoresistance (TMR).

Impedance spectroscopy of micron sized magnetic tunnel junctions with MgO tunnel barrier

“…2 They have also found applications in magnetic microscopy. 3 Recently, ac impedance spectroscopy of the MTJs has received considerable interest because the above mentioned applications require high speed functionality and small devices ͑Al-oxide tunnel barriers, [4][5][6][7] MgO tunnel barriers, 8,9 at least one electrode nonmagnetic͒. 10,11 All of these studies dealt with "large area" devices of ϳ1000 m 2 or larger.…”