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Increasing the performance of a superconducting spin valve using a Heusler alloy
2018, Kamashev, A.A., Validov, A.A., Schumann, J., Kataev, V., Büchner, B., Fominov, Y.V., Garifullin, I.A.
We have studied superconducting properties of spin-valve thin-layer heterostructures CoOx/F1/Cu/F2/Cu/Pb in which the ferromagnetic F1 layer was made of Permalloy while for the F2 layer we have taken a specially prepared film of the Heusler alloy Co2Cr1-xFexAl with a small degree of spin polarization of the conduction band. The heterostructures demonstrate a significant superconducting spin-valve effect, i.e., a complete switching on and offof the superconducting current flowing through the system by manipulating the mutual orientations of the magnetization of the F1 and F2 layers. The magnitude of the effect is doubled in comparison with the previously studied analogous multilayers with the F2 layer made of the strong ferromagnet Fe. Theoretical analysis shows that a drastic enhancement of the switching effect is due to a smaller exchange field in the heterostructure coming from the Heusler film as compared to Fe. This enables to approach an almost ideal theoretical magnitude of the switching in the Heusler-based multilayer with a F2 layer thickness of ca. 1 nm. © 2018 Kamashev et al.
Niederdimensionale thermoelektrische Materialien auf der Basis halbleitender Silizide und Silizium/Germanium-Übergittern : Abschlußbericht zum Verbundvorhaben Niederdimensionale thermoelektrische Materialien für Energiewandler
2003, Heinrich, Armin, Schumann, J.
[no abstract available]
Superconducting switching due to a triplet component in the Pb/Cu/Ni/Cu/Co2Cr1-xFexAly spin-valve structure
2019, Kamashev, A.A., Garif'yanov, N.N., Validov, A.A., Schumann, J., Kataev, V., Büchner, B., Fominov, Y.V., Garifullin, I.A.
We report the superconducting properties of the Co2Cr1-xFexAly/Cu/Ni/Cu/Pb spin-valve structure the magnetic part of which comprises the Heusler alloy layer HA = Co2Cr1-xFexAly with a high degree of spin polarization (DSP) of the conduction band and a Ni layer of variable thickness. The separation between the superconducting transition curves measured for the parallel (α = 0°) and perpendicular (α = 90°) orientation of the magnetization of the HA and the Ni layers reaches up to 0.5 K (α is the angle between the magnetization of two ferromagnetic layers). For all studied samples the dependence of the superconducting transition temperature Tc on α demonstrates a deep minimum in the vicinity of the perpendicular configuration of the magnetizations. This suggests that the observed minimum and the corresponding full switching effect of the spin valve is caused by the long-range triplet component of the superconducting condensate in the multilayer. Such a large effect can be attributed to a half-metallic nature of the HA layer, which in the orthogonal configuration efficiently draws off the spin-polarized Cooper pairs from the space between the HA and Ni layers. Our results indicate a significant potential of the concept of a superconducting spin-valve multilayer comprising a half-metallic ferromagnet, recently proposed by A. Singh et al., Phys. Rev. X 2015, 5, 021019, in achieving large values of the switching effect.
Materialentwicklung für thermoelektrische Dünnschichtsysteme auf der Basis von Silizid- und Skutteruditverbindungen : Abschlussbericht
2003, Schumann, J.
[no abstract available]
Hochstabile elektrische Funktionsschichten für miniaturisierte Chipbauelemente : IFW-Teilbericht für das Verbundvorhaben: Neue Keramik- und Dünnschichtwerkstoffe für miniaturisierte Chipbauelemente
1999, Brüstel, U., Heinrich, A., Schumann, J., Vinzelberg, H.
[no abstract available]