High emission power and Q factor in spin torque vortex oscillator consisting of FeB free layer

Microwave oscillation properties of spin torque vortex oscillators (STVOs) consisting of an FeB vortex free layer were investigated. Because of a high MR ratio and large DC current, a high emission power up to 3.6 mu W was attained in the STVO with a thin FeB free layer of 3 nm. In STOs with a thicker FeB layer, e.g., 10 nm thick, we obtained a large Q factor greater than 6400 while maintaining a large integrated emission power of 1.4 mu W. Such excellent microwave performance is a breakthrough for the mutual phase locking of STVOs by electrical coupling. (C) 2014 The Japan Society of Applied Physics