Dynamic state transitions in vortex-based magnetic tunnel junctions for high frequency data transmission

Abstract

Vortex-based spin torque nano-oscillators (STNOs) are nanoscale tunable multifunctional radio-frequency devices which have been proposed for a diverse variety of applications, ranging from novel wireless communications paradigms [1, 2], random number generators [3] and more recently the building blocks of novel bio-inspired computing architectures for neuromorphic computing [4]. The competitiveness of STNOs as an emerging technology lies in several key characteristics relative to conventional electronics, including tunability, multi-functionality, scalability and radiation hardness. Vortex-based STNOs have been shown to demonstrate superior performance parameters in terms of output power emission and signal linewidth to other STNO-based radio frequency devices, operating in the 50 MHz to 1 GHz regime.By harnessing the rich dynamics associated with non-homogeneous magnetisation configurations in confined nanostructures, the free layer of a magnetic tunnel junction (MTJ) can be forced, via a localised magnetic field, to transition between two magnetic states: the quasi-uniform and vortex states. In this report we demonstrate that such transitions can be driven back and forth to a dynamic equilibrium by exciting an MTJ with alternating magnetic fields close to the resonant modes of the magnetic vortex. The induced magnetic state transitions leads to a strong dependence of the resistance of the MTJ to the incoming signal, resulting in nominally identical devices which can act as both high frequency sources and detectors. In this presentation we will show how this dynamic behaviour can have exciting potential for future emerging paradigms, such as novel analogue wideband communication, integrated rf source/sensors and the building blocks for neuromorphic computing architectures. **