Scattering of conduction electrons in Fe(t x , Å)/Cr(10 Å) superlattices with ultrathin iron layers

IR magnetoreflection spectra, diagonal σ _xx and off-diagonal σ _xy components of the effective optical conductivity tensor, and magnetic properties of Fe(t _x , Å)/Cr(10 Å) superlattices have been studied. The abrupt decrease in the amplitude of dissipative function ?ωImσ _xy (ω) (ω is the cyclic frequency of light wave) in the superlattices with ultrathin Fe layers (t _Fe = 3.2, 2.6, 2.1 Å) has been analyzed. It has been found that the magnetorefractive effect in nanostructures with ultrathin iron layers is due to scattering of conduction electrons by magnetic interfacial layers formed in the Cr matrix with complete consumption of deposited iron atoms. The parameters of the interfacial scattering of electrons in the spin-up (└) and spin-down (┌) conduction channels have been discussed.     

Microstrip superheterodyne coherent microwave bridge

Reasons for unsatisfactory operation of the superheterodyne spectrometers at increased microwave power are considered. Recommendations for designing the superheterodyne microwave bridge of the EPR spectrometer working at the microwave power of about hundreds of milliwatt are given. These recommendations allow one to develop the spectrometer comparable to those with modulation of resonant conditions concerning reliability, stability and simplicity of operation. The experimental prototype of the coherent microwave bridge of the X-band superheterodyne EPR spectrometer with the intermediate frequency of 100 MHz is described. The microwave circuit of the bridge is assembled using microstrip hybrid integrated circuits and requires no adjustment in operation. The microwave Gunn-diode generators with the electronic tuning stabilized by dielectric resonators are used. The dynamic range of 54 dB at the maximum power of 40 mW is reached. As the microwave power increases up to the maximum value, no tendency to the degration of sensitivity equal to 5·10^?11 W at the 40 MHz band is noticed.     

On almost good triples of vertices in edge regular graphs

Consider a connected edge regular graph Γ with parameters (v, k, λ) and put b ₁ = k?λ?1. A triple (u, w, z) of vertices is called (almost) good whenever d(u, w) = d(u, z) = 2 and µ(u, w)+µ(u, z) ≤ 2k ? 4b ₁ + 3 (and µ(u, w) + µ(u, z) = 2k ? 4b ₁ + 4). If k = 3b ₁ + γ with γ ≥ ?2, a triple (u, w, z) is almost good, and Δ = [u] ∩ [w] ∩ [z] then: either |Δ| ≤ 2; or Δ is a 3-clique and Γ is a Clebsch graph; or Δ is a 3-clique, k = 16, b ₁ = 6, and v = 31; or Δ is a 4-clique and Γ is a Schläfli graph.