Control and Optimization of Coherence of a Nano-sized Spin-torque Microwave Oscillator for Military Nano- Electronics

A theory of generation linewidth of a spin-torque oscillator (STO) based on an in-plane magnetized nanopillar with an anisotropic “free” magnetic layer has been developed. It is shown that the coherent properties of microwave generation strongly depend on the direction and magnitude of the in-plane bias magnetic field. In particular, it is predicted that by choosing the direction of the bias field 0 H along the “hard” anisotropy axis of the STO “free” layer and the magnitude of this field to be four times larger than the anisotropy field A H ( A H H 4 0 = ) it would be possible to compensate the nonlinear phase noise and to achieve the minimum value of the generation linewidth, characteristic for an autooscillator without a nonlinear frequency shift. The developed theory of STO creates a possibility to unite nano-magnetism and microwave theory, and to develop a basis for a novel nano-spintronic microwave technology – the technology of nano-sized tunable microwave oscillators that are insensitive to ionizing radiation and, therefore, are suitable for applications in the future military nano-electronic integrated circuits.