Analysis of Electromagnetic Fields Generated by a Spin-Torque Oscillator

Electromagnetic fields generated by spin-torque nano-oscillators have been theoretically investigated. The study is conducted on a specific magnetic device with an in-plane magnetization rotation driven by spin transfer torque. Under the macrospin approximation, analytic solutions of the electromagnetic fields can be obtained. The electromagnetic fields have been analyzed and characterized in the near field and far regimes. In the far field, the electromagnetic fields resemble those of an electric dipole. However, the radiating fields are too weak to be detected, given the small size of the spin-torque oscillator. In the near field, the magnetic dipole field from the rotating magnetization and a radiating E-field are detectable over a reasonable range. This implies that the spin-torque oscillators can be used as a magnetic field or an electric field source in a short-range communication system.