Improved Electrochemical Performance Based on Nanostructured SnS_2@CoS_2–rGO Composite Anode for Sodium-Ion Batteries

A promising anode material composed of SnS_2@CoS_2 flower-like spheres assembled from SnS_2 nanosheets and CoS_2 nanoparticles accompanied by reduced graphene oxide(rGO) was fabricated by a facile hydrothermal pathway. The presence of rGO and the combined merits of SnS_2 and CoS_2 endow the SnS_2@-CoS_2–rGO composite with high conductivity pathways and channels for electrons and with excellent properties as an anode material for sodium-ion batteries(SIBs). A high capacity of 514.0 mAh g^(-1) at a current density of200 m A g^(-1) after 100 cycles and a good rate capability can be delivered. The defined structure and good sodium-storage performance of the SnS_2@CoS_2–rGO composite demonstrate its promising application in high-performance SIBs.

Improvement of high-frequency properties of Co2FeSi Heusler films by ultrathin Ru underlayer

Heusler Co2FeSi films with a uniaxial magnetic anisotropy and high ferromagnetic resonance frequency fr were deposited by an oblique sputtering technique on Ru underlayers with various thicknesses tRufrom 0 nm to 5 nm.It is revealed that the Ru underlayers reduce the grain size of Co2FeSi,dramatically enhance the magnetic anisotropy field HK induced by the internal stress from 242 Oe(1 Oe=79.5775 A·m^-1)to 582 Oe with an increment ratio of 2.4,while a low damping coefficient remains.The result of damping implies that the continuous interface between Ru and Co2FeSi induces a large in-plane anisotropic field without introducing additional external damping.As a result,excellent high-frequency soft magnetic properties with fr up to 6.69 GHz are achieved.

Effect of interface magnetization depinning on the frequency shift of ferromagnetic and spin wave resonance in YIG/GGG films

Nowadays the yttrium iron garnet(Y3Fe5O12, YIG) films are widely used in the microwave and spin wave devices due to their low damping constant and long propagation distance for spin waves. However, the performances, especially the frequency stability, are seriously affected by the relaxation of the interface magnetic moments. In this study, the effect of out-of-plane magnetization depinning on the resonance frequency shift(△ fr) was investigated for 3-μm YIG films grown on Gd3Ga5O12(GGG)(111) substrates by liquid-phase epitaxy. It is revealed that the ferromagnetic resonance(FMR) and spin wave propagation exhibit a very slow relaxation with relaxation time τ even longer than one hour under an out-of-plane external magnetic bias field. The △ fr span of 15.15–24.70 MHz is observed in out-of-plane FMR and forward volume spin waves. Moreover, the △ fr and τ depend on the magnetic field. The △ fr can be attributed to that the magnetic moments break away from the pinning layer at the YIG/GGG interface. The thickness of the pinning layer is estimated to be about9.48 nm to 15.46 nm according to the frequency shifting. These results indicate that △ fr caused by the pinning layer should be addressed in the design of microwave and spin wave devices, especially in the transverse magnetic components.