N. Barros, H. Rassam, H. Kachkachi
We analytically determine the optimal microwave field allowing to reverse the magnetic moment of a nanomagnet modeled as a macrospin. This is done by minimizing the total injected energy. The optimal field is found to be modulated both in amplitude and frequency, and orthogonal to the magnetic moment at any time. Its peculiar shape is directly related to the energy landscape (anisotropy, applied field) and to the damping parameter. For typical values of the damping parameter, a weak microwave field is sufficient to induce switching. The results are in good agreement with the fields previously obtained using the optimal control theory. The total injected energy is found to be proportional to the static energy barrier between the initial state and the saddle point and to the damping parameter. This result may be used as a means for probing the damping parameter and surface effects in real nanoparticles.
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http://arxiv.org/abs/1303.3501
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