N°19 - 23 September 2016 - SPIN TORQUE RESONANT EXPULSION OF THE VORTEX CORE FOR AN EFFICIENT RADIO-FREQUENCY DETECTION SCHEME
Spin-polarised radio-frequency currents, whose frequency is equal to that of the gyrotropic mode, will cause an excitation of the core of a magnetic vortex confined in a magnetic tunnel junction. When the excitation radius of the vortex core is greater than that of the junction radius, vortex core expulsion is observed, leading to a large change in resistance, as the layer enters a predominantly uniform magnetisation state. Unlike the conventional spin-torque diode effect, this highly tunable resonant effect will generate a voltage which does not decrease as a function of rf power, and has the potential to form the basis of a new generation of tunable nanoscale radio-frequency detectors.
Nature Nanotech 11, 360-364 (2016)
Figure 1: Radio frequency current dependence. a,b, The rectified voltage for observed for the core expulsion (a) and the spin-torque diode measurements (b) taken at 6 and 0 mA, respectively, for IRF = 0.2 mA. c, The generated voltage, ΔV as a function of IRF for a range of d.c. currents at Hperp = 150 mT and θH = 90.1°. The core expulsion shows a constant ΔV as a function of IRF, whereas the resonant excitation decreases linearly with IRF.