The giant spin blocking of tunnel currents discovered by us (Low. Temp. Phys. 36, 186 (2010)) is investigated theoretically and experimentally in ferromagnet F (Co2CrAl)- insulator I- superconductor S (Pb) heterostructures with a wide range of specific resistances (10−7–10−4 Ω · cm2). The magnitude of this effect is found to depend on the specific resistance of the junction in the normal state and on recombination spin depolarization. A theoretical model which provides an adequate description of the tunnelling of spin-polarized electrons in F-I-S junctions is proposed. It is found that the normalized conductivity σFS of an F-I-S tunnel junction can be considerably lower than the fundamental normalized conductivity σNS of an N-I-S junction (where N is a normal metal). The proposed model is used to estimate the degree of spin polarization p of films of the ferromagnetic semimetal Co2CrAl (Heusler alloy) with B2- and L21-type crystal structures, which is close to 1 (p ≈ 0.97). The temperature dependence σFS(T) of a Co2CrAl-I-Pb F-I-S tunnel junction is studied experimentally. A theoretical model is proposed which provides an adequate description of the temperature behavior of the normalized conductivity σFS(T) with features of spin-polarized tunnelling taken into account.
Tunnel spin injection and the conductivity of ferromagnet-superconductor heterostructures with zero bias
E. M. Rudenko, I. V. Korotash, Yu. V. Shlapak, Y. V. Kudryavtsev, A. A. Krakovny, M. V. Dyakin; Tunnel spin injection and the conductivity of ferromagnet-superconductor heterostructures with zero bias. Low Temp. Phys. 1 June 2011; 37 (6): 489–495. https://doi.org/10.1063/1.3620864
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