Mode-hopping mechanism generating colored noise in a magnetic tunnel junction based spin torque oscillator

Sharma, Raghav, Dürrenfeld, P., Iacocca, Ezio, Heinonen, O. G., Åkerman, J. and Muduli, P. K. (2014) Mode-hopping mechanism generating colored noise in a magnetic tunnel junction based spin torque oscillator. Applied Physics Letters, 105 (13). p. 132404. ISSN 0003-6951

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Abstract

The frequency noise spectrum of a magnetic tunnel junction based spin torque oscillator is examined where multiple modes and mode-hopping events are observed. The frequency noise spectrum is found to consist of both white noise and 1/f frequency noise. We find a systematic and similar dependence of both white noise and 1/f frequency noise on bias current and the relative angle between the reference and free layers, which changes the effective damping and hence the mode-hopping behavior in this system. The frequency at which the 1/f frequency noise changes to white noise increases as the free layer is aligned away from the anti-parallel orientation w.r.t the reference layer. These results indicate that the origin of 1/f frequency noise is related to mode-hopping, which produces both white noise as well as 1/f frequency noise similar to the case of ring lasers.

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