Microwave-induced spin-flip scattering of electrons in point contacts

In bilayer systems, electron-hole (e-h) pairs, we investigate resonant interaction of conduction electrons with an electromagnetic field that irradiates a point contact between a ferromagnetic and a normal metal in the presence of a strong magnetic field of order 1 T. We show that electron spin-flips caused by resonant absorption and stimulated emission of photons result in a sharp peak in the magnetic-field dependence of the point-contact resistance. The height of the peak is shown to be directly proportional to the net rate of energy transfer to the electromagnetic field in the point contact due to absorption and stimulated emission of photons. Estimations indicate that our theory can serve as a basis for the explanation of recent experiments [A.M. Kadigrobov , New J. Phys. 13, 023007 (2011)]. (C) 2012 American Institute of Physics. [doi: 10.1063/1.3671676]