Fabrication of Spin-Transfer Nano-Oscillator by Colloidal Lithography

We fabricate nanoscale spin-transfer oscillators (STOs) by utilizing colloidal nanoparticles as a lithographic mask. By this approach, high quality STO devices can be fabricated, and as an example the fabricated STO devices using MgO magnetic tunnel junction as the basic cell exhibit current-induced microwave emission with a large frequency tunability of 0.22GHz/mA. Compared to the conventional approaches that involve a step of defining nanoscale elements by means of electron beam lithography, which is not readily available for many groups, our strategy for STO fabrication does not require the sophisticated equipment (similar to million dollars per unit) and expensive lithography resist, while being cost-effective and easy to use in laboratory level. This will accelerate efforts to implement STO into on-chip integrated high-radio frequency applications.