Composite magnetic tunnel junctions for fast memory devices and efficient spin-torque nano-oscillators

We investigate a possibility to use composite magnetic tunnel junction structures (MTJs) to compose fast memory devices and efficient spin-torque nano-oscillators. In terms of magnetic memory, we study the switching statistics dependence on memory cell geometry by means of systematic micromagnetic simulations. We find that MTJs with a free layer composed of two ellipses with the axes a/2 > b inscribed into a rectangle a × b demonstrate a substantial decrease of the switching time and the switching current as compared to conventional MTJs with a monolithic free layer. In terms of the spin-torque nano-oscillator we propose a novel structure based on two MgO-MTJs with a shared free layer. By performing extensive micromagnetic modeling, we found that the structure exhibits a wide tunability of oscillation frequencies from a few gigahertz to several ten gigahertz.