2020, Tan, Li, Wang, Fan, Zhang, Peipe, Suzuki, Yuichi, Wu, Yingquan, Chen, Jiangang, Yang, Guohui, Tsubaki, Noritatsu

An elegant catalyst is designedviathe encapsulation of metallic oxide Zn-Cr inside of zeolite SAPO34 as a core-shell structure (Zn-Cr@SAPO) to realize the coupling of methanol-synthesis and methanol-to-olefin reactions. It can not only break through the limitation of the Anderson-Schulz-Flory distribution but can also overcome the disadvantages of physical mixture catalysts, such as excessive CO2formation. The confinement effect, hierarchical structure and extremely short distance between the two active components result in the Zn-Cr@SAPO capsule catalyst having better mass transfer and diffusion with a boosted synergistic effect. Due to the difference between the adsorption energies of the Zn-Cr metallic oxide/SAPO zeolite physical mixture and capsule catalysts, the produced water and light olefins are easily removed from the Zn-Cr@SAPO capsule catalyst after formation, suppressing the side reactions. The light olefin space time yield (STY) of the capsule catalyst is more than twice that of the typical physical mixture catalyst. The designed capsule catalyst has superior potential for scale-up in industrial applications while simultaneously extending the capabilities of hybrid catalysts for other tandem catalysis reactions through this strategy. © The Royal Society of Chemistry 2020.

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.

2018, Ghunaim, R., Scholz, M., Damm, C., Rellinghaus, B., Klingeler, R., Büchner, B., Mertig, M., Hampel, S.

In the present work, we demonstrate different synthesis procedures for filling carbon nanotubes (CNTs) with equimolar binary nanoparticles of the type Fe-Co. The CNTs act as templates for the encapsulation of magnetic nanoparticles and provide a protective shield against oxidation as well as prevent nanoparticle agglomeration. By variation of the reaction parameters, we were able to tailor the sample purity, degree of filling, the composition and size of the filling particles, and therefore, the magnetic properties. The samples were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), superconducting quantum interference device (SQUID) and thermogravimetric analysis (TGA). The Fe-Co-filled CNTs show significant enhancement in the coercive field as compared to the corresponding bulk material, which make them excellent candidates for several applications such as magnetic storage devices.

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.