Low Voltage Reversible Manipulation of Ferromagnetic Resonance Response in CoFeB/HfO_2 Heterostructures

We report that the ferromagnetic resonance (FMR) response of the CoFeB/HfO_2 heterostructures is stabilized and reversibly manipulated by ionic gel. Ionic gel with excellent flexibility is used as a medium to form an electric field. When a 4 V gate voltage is applied, the resonance field H_\rm r and peak-to-peak linewidth \Delta H_\rm pp at different angles are regulated. When \theta = 20^\circ, the H_\rm r is regulated up to 82 Oe. When \theta = 70^\circ, \Delta H_\rm pp is tuned up to 75 Oe. When the gate voltage is repeatedly applied, the FMR spectra can be freely switched between the initial state and the gated state. Our study provides an effective method to manipulate the damping of the magnetic film stably and reversibly.