Transitions of the magnetization in the presence of a polarized current

• Published in: Journal of magnetism and magnetic materials Vol. 468; pp. 185 - 187
• Main Author: Simanjuntak, Herbert P.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15.12.2018; Elsevier BV
• Subjects: Equations of motion; Ferromagnetism; Magnetism; Magnetization; Magnetization switching; Metastable state; Metastable states; Spintronics; Temperature; Transition rates; Transition rates; Metastable states; Magnetization switching; Spintronics
• ISSN: 0304-8853; 1873-4766
• DOI: 10.1016/j.jmmm.2018.08.008

•The work considers macroscopic quantum phenomena of the magnetization in spintronic systems.•Transitions of the magnetization from a metastable state to a more stable one is calculated in the presence of a polarized current.•The sign of the current determines the type of dissipation involved in the transitions.•The rates of transitions are given from low to high temperatures with or without dissipation.•It is shown that the rate of transitions is low at low temperatures and vanishes at zero temperature which leaves the magnetization relatively stable in a metastable minimum.•This is different than the usual case without the presence of a polarized current where the rate of transitions does not vanish even at zero temperature. Transitions of the magnetization out of a metastable state to a more stable one in the presence of a polarized current is considered. We derive an effective Lagrangian to represent the equation of motion of the magnetization, and with the method of path integral we derive the imaginary-time action and the rate of transitions out of the metastable state. As the current can be varied, its presence allows one to study transitions of the magnetization with or without dissipation. The rates of quantum and thermal transitions are given for various regimes of temperature. Results for cubic and tetragonal ferromagnets are given as examples.