Dipolar Field Effect on Microwave Oscillation in a Domain-Wall Spin Valve

In this paper, we examined dipolar field effects on the microwave generation in the domain-wall spin valve by solving simultaneously the Landau-Lifshitz-Gilbert and Zhang-Levy-Fert diffusion equations. By numerically analyzing dipolar field dependence, we showed that the microwave generation needs the dipole-dipole interaction for a 180^deg domain wall and the amplitude of the microwave voltage signal depends strongly on the exchange length. In order to design a microwave generator using the domain-wall spin valve with high efficiency, we propose that the materials with short exchange length are preferred.