05 novembre 2010

Micromagnetic simulation showing the formation of a mobile vortex state (blue) in the spintronic oscilator. At the center of the vortex the magnetization is perpendicular to the disk.

Spintec has discovered and patented a new technology to fabricate spintronic oscillators, which have high purity radiofrequency emissions several hundred times more powerful than that of traditional oscillators.


The magnetization of junctions from this new process, the precession amplitude under a small magnetic field and a high DC current, is much larger than for junctions used previously in spintronic oscillators. This is due to the formation of a rotating vortex state in the oscillator because of the spin transfer torque. The fundamental frequency is 400MHz, compared to a few GHz of existing spintronic oscillators. The spectral width is only 1MHz, and the amplitude of the harmonics is also reduced. Initially, the process had been developed to reduce the resistance of magnetic tunnel junctions which were to be used as sensors in magnetic read heads for hard disk drives.


Another benefit of the technology is that these oscillators can be synchronized: applying a current with a frequency double that of the natural frequency makes it possible to further increase the oscillation amplitude and lower the frequency line width to a few kHz. This parametric amplification is comparable to the way children and adults sway a swing in the playground. Moving the legs forward or backwards displaces the center of mass as the swing movement changes direction, i.e., twice in a swing period. It is possible to use the second harmonic of the oscillator to achieve higher emitting power through self-synchronization. 


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