Nonlinear effective spin-mixing conductance in Pt/Ni80Fe20/Pt thin films

In this study, the effective spin-mixing conductance in Ni80Fe20/Pt was investigated by measuring the interface-induced enhancement of the Gilbert damping constant. Ferromagnetic resonance spectra were measured in coplanar waveguide geometry with different incident microwave powers. The nonlinear behavior of normal Gilbert damping G(0) and effective spin-mixing conductance g.. have been observed when the incident microwave power is above a critical ac field h(rf) of 1.6 Oe. Both phenomena are explained by considering the coupling between spin coherent precession and spin wave modes. This work demonstrates the nonlinear behavior of the effective spin-mixing conductance g(up down arrow). It suggests that the nonlinear spin wave modes excited at high incident microwave power are detrimental to the spin pumping effect and should be avoided in future spin battery designs. The capability of tuning G0 and g(up down arrow) through the microwave power is also useful for the fundamental study on the damping mechanism. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3072443]