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Photon generation in ferromagnetic point contacts
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View: Figures


Image of FIG. 1.
FIG. 1.

Diffusive point contact under irradiation. A voltage bias V injects a spin-polarized current from ferromagnetic metal 1 with magnetic moment M 1 into ferromagnetic metal 2 with magnetic moment M 2. A spin-up electron is shown to move along a diffusive trajectory from metal 1 to metal 2 (red line a) where it resonantly interacts with the electromagnetic field, which results in a spin-flip and the emission of a photon. Continuing along its diffusive path with spin down (blue line b), the spin-dependent contact resistance implies that the radiation-induced spin-flip contributes to a change of the magnetoresistance of the point contact.

Image of FIG. 2.
FIG. 2.

Zero-temperature energy distributions for (a) magnetic moment-up (spin-down), f p , and (b) magnetic moment-down (spin-up) electrons, f p , at point r in ferromagnetic metal 2 of the point contact. The inset (c) shows the Zeeman energy splitting and the magnetization direction M 2. All states are occupied up to ε = ε f  − eV/2 − I and ε = ε f  − eV/2 + I, respectively (blue rectangles, 1), but in the intervals (ε, ε + eV) and (ε, ε + eV) the states are only partly occupied (red rectangles, 2) and to an extent that is determined by the probabilities α p (r) and α p (r) for “hot” electrons in the ferromagnetic metal to reach r. Clearly, the difference between the densities of spin-down and spin-up electrons, n (r) − n (r) ∝ [(α (2) − α (2))eV − 2I], depends on the bias voltage V. It follows that the spin population can be inverted, so that n (r) > n (r), for large enough V if α (2) > α (2).

Image of FIG. 3.
FIG. 3.

Dependence of the relative resistance change under irradiation on the irradiation frequency ω normalized by the electron spin-flip relaxation frequency νsf for νsf /I = 10−1 (here I is the exchange energy).


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Photon generation in ferromagnetic point contacts