Role of spin-transfer torques on synchronization and resonance phenomena in stochastic magnetic oscillators

• Published in: Journal of applied physics Vol. 120; no. 9
• Main Authors: Accioly, Artur, Locatelli, Nicolas, Mizrahi, Alice, Querlioz, Damien, Pereira, Luis G., Grollier, Julie, Kim, Joo-Von
• Format: Journal Article
• Language: English
• Published: Melville American Institute of Physics 07.09.2016
• Subjects: Alternating current; Applied physics; CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; DAMPING; EFFICIENCY; ELECTRIC CURRENTS; Electrical junctions; FLUCTUATIONS; LAYERS; Magnetic resonance; MAGNETIZATION; NOISE; OSCILLATORS; RESONANCE; SPIN; STOCHASTIC PROCESSES; Stochastic resonance; SUPERPARAMAGNETISM; Synchronism; SYNCHRONIZATION; TORQUE; Tunnel junctions; Variation
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.4962015

A theoretical study on how synchronization and resonance-like phenomena in superparamagnetic tunnel junctions can be driven by spin-transfer torques is presented. We examine the magnetization of a superparamagnetic free layer that reverses randomly between two well-defined orientations due to thermal fluctuations, acting as a stochastic oscillator. When subject to an external ac forcing, this system can present stochastic resonance and noise-enhanced synchronization. We focus on the roles of the mutually perpendicular damping-like and field-like torques, showing that the response of the system is very different at low and high frequencies. We also demonstrate that the field-like torque can increase the efficiency of the current-driven forcing, especially at sub-threshold electric currents. These results can be useful for possible low-power, more energy efficient applications.