Influence of MgO tunnel barrier thickness on spin-transfer ferromagnetic resonance and torque in magnetic tunnel junctions

Abstract

Spin-transfer ferromagnetic resonance (ST-FMR) in symmetric magnetic tunnel junctions (MTJs) with a varied thickness of the MgO tunnel barrier (0.75 nm < $t_{MgO}$ < 1.05 nm) is studied using the spin-torque diode effect. The application of an RF current into nanosized MTJs generates a DC mixing voltage across the device when the frequency is in resonance with the resistance oscillations arising from the spin transfer torque. Magnetization precession in the free and reference layers of the MTJs is analyzed by comparing ST-FMR signals with macrospin and micromagnetic simulations. From ST-FMR spectra at different DC bias voltage, the in-plane and perpendicular torkances are derived. The experiments and free-electron model calculations show that the absolute torque values are independent of tunnel barrier thickness. The influence of coupling between the free and reference layer of the MTJs on the ST-FMR signals and the derived torkances are discussed.

6 pages, 5 figures

References in corpus (5)

• Bias-driven large power microwave emission from MgO-based tunnel magnetoresistance devices
• Spin-transfer-driven ferromagnetic resonance of individual nanomagnets
• Excitations of incoherent spin-waves due to spin-transfer torque
• Ab initio studies of the spin-transfer torque in tunnel junctions
• Spin transfer torque oscillator based on asymmetric magnetic tunnel junctions

Cited by in corpus (4)

• Spin-torque diode radio-frequency detector with voltage tuned resonance
• Rectification of radio frequency current in giant magnetoresistance spin valve
• Backhopping effect in magnetic tunnel junctions: comparison between theory and experiment
• Influence of image forces on the interlayer exchange interaction in magnetic tunnel junctions with ferroelectric barrier