Symmetry ensemble theory of spin wave emitting effectdriven by current in nanoscale magnetic multilayer

This paper proposes a symmetry ensemble model for the magneticdynamics caused by spin transfer torque in nanoscalepseudo-spin-valves, in which individual spin moments in the freelayer are considered as subsystems to form a spinor ensemble. Themagnetization dynamics equation of the ensemble was developed. Byanalytically investigating the equation, many magnetization dynamicsproperties excited by polarized current reported in experiments,such as double spin wave modes and the abrupt frequency jump, can besuccessfully explained. It is pointed out that an external field isnot necessary for spin wave emitting (SWE) and a novel perpendicularconfiguration structure can provide much higher SWE efficiency inzero magnetic field.