Microwave Signal Generation in Single-Layer Nano-Contact Spin Torque Oscillators

• Published in: IEEE transactions on magnetics Vol. 49; no. 7; pp. 4331 - 4334
• Main Authors: Sani, Sohrab Redjai, Durrenfeld, Philipp, Mohseni, Seyed Majid, Chung, Sunjae, Akerman, Johan
• Format: Journal Article Conference Proceeding
• Language: English
• Published: New York, NY IEEE 01.07.2013; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Cross-disciplinary physics: materials science; rheology; DRIVEN; Exact sciences and technology; Fysik; Magnetic hysteresis; Magnetism; Materials science; Microwave devices; Microwave measurement; Microwave oscillators; Other topics in materials science; Physical Sciences; Physics; POLARIZED CURRENT; Single layer; spin torque oscillator; Torque; vortex; vortex; Microwave radiation; Single layer; Oscillators; spin torque oscillator; Magnetic properties
• ISSN: 0018-9464; 1941-0069; 1941-0069
• DOI: 10.1109/TMAG.2013.2250931

We demonstrate spin transfer torque (STT) driven microwave signal generation, from about 250 MHz to above 3 GHz, in single permalloy layers underneath a nano-contact with diameter of 100 nm. The threshold current for signal generation is found to be strongly hysteretic, the microwave signal shows a number of harmonics, zero-field operation is straightforward, and the microwave frequency increases quasi-linearly with drive current. All observations are consistent with STT driven motion of a vortex-antivortex pair nucleated by the Oersted field underneath the nano-contact. While the generated power is about 10 dB smaller than the best GMR based nanocontact spin torque oscillators, the linewidth of 6-100 MHz is of the same order.