Stimulated emission and absorption of photons in magnetic point contacts

Abstract

Point contacts between high anisotropy ferromagnetic SmCo 5 and normal metal Cu are used to achieve a strong spin-population inversion in the contact core. Subjected to microwave irradiation in resonance with the Zeeman splitting in Cu, the inverted spin population relaxes through stimulated spin-flip photon emission, detected as peaks in the point-contact resistance. Resonant

Sub-10 nm colloidal lithography for circuit-integrated spin-photo-electronic devices

“…The material combination was selected to represent the spin-injection laser device [15,24–25], and consisted of a spin-majority/minority ferromagnetic bi-layer Fe 0.7 Cr 0.3 (10 nm)/Fe(15 nm) [25] capped with Cu(10 nm), for spin-population-inversion injection. Even though the deposition technique is not highly directional, we find that the angle of incidence through the 10 nm openings in the mask (angle between the normal to the sample surface and the normal to the sputtering target surface) is an important parameter determining the size of the resulting point contacts: the closer to normal incidence the closer the resulting contact size to the mask feature size (normal incidence), and the larger the angle of incidence the deeper below 10 nm the nanocontacts are due to the double shadowing effect illustrated in Fig.…”

“…Another interesting application of the spin-majority/minority Fe/Fe 0.7 Cr 0.3 contact-core material used above is the spin-flip photon-emission effect [15,24–25], which requires spin-polarized and energetically nonequilibrium injection and, therefore, near-ballistic point-contact arrays. The energetics of the process is illustrated in the inset to Fig.…”

“…5, where the spin-majority carriers from the Fe injector create spin-population inversion in the spin-minority FeCr, relaxing through emission of terahertz or infrared (IR) photons. To achieve this we have performed fabrication at the limit of the etching and angle-deposition parameters discussed above, for deep sub-10 nm point-contact size and a smaller operating fraction of the array, so that the injection voltage per contact is greater than the exchange splitting in the ferromagnetic point contact core (10–100 mV, see [24–25] for more details). Such high-bias, high-density, spin-polarized injection produces large nonequilibrium spin accumulation in the contact core, which allows spin-flip photon-emission transitions, vertical in the momentum of the electron.…”

Wurtzite spin lasers

“…They enable depositing a thin-film ferromagnet just 100-200 nm away from the gain region for spin injection at the room temperature. Various spin and phonon lasers can also be implemented using intraband transitions within the conduction band [77] or in metallic systems [78,79]. It would be interesting to develop a suitable description for them by combining microscopic gain calculations and simple rate equations.…”

Photon generation in ferromagnetic point contacts

“…A significant nonequilibrium spin accumulation together with a highly inverted population of the spin-split electron levels such as may occur in nanosized heterocontacts between nonidentical magnets or in point contacts between a magnetic and a normal metal subject to an external magnetic field [10][11][12][13][14] offers a new area of research. Such an inverse level population makes it possible for the electrons to relax by a radiative spin-flip transition from the upper to the lower spin level as a photon is emitted.…”