Robustness of the0−πtransition against compositional and structural ageing in superconductor/ferromagnetic/superconductor heterostructures

Abstract

We have studied the temperature induced 0 − π thermodynamic transition in Nb/PdNi/Nb Superconductor/Ferromagnetic/Superconductor (SFS) heterostructures by microwave measurements of the superfluid density. We have observed a shift in the transition temperature with the ageing of the heterostructures, suggesting that structural and/or chemical changes took place. Motivated by the electrodynamics findings, we have extensively studied the local structural properties of the samples by means of X-ray Absorption Spectroscopy (XAS) technique, and the compositional profile by Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS). We found that the samples have indeed changed their properties, in particular for what concerns the interfaces and the composition of the ferromagnetic alloy layer. The structural and compositional data are consistent with the shift of the 0 − π transition toward the behaviour of heterostructures with different F layers. An important emerging indication to the physics of SFS is the weak relevance of the ideality of the interfaces: even in aged samples, with less-than-ideal interfaces, the temperature-induced 0 − π transition is still detectable albeit at a different critical F thickness.

Advances in Structural and Morphological Characterization of Thin Magnetic Films: A Review

“…Furthermore, by using advanced liquid-metal ion guns (LMIGs), one can reach a lateral resolution of about 100 nm for elemental detection (ToF-SIMS imaging). The average lateral resolution obtained is <50 nm with a depth resolution of <10 nm [67,69,[131][132][133][134][135][136][137]. For thin films, static ToF-SIMS is helpful to detect any kind of inhomogeneity and defects on the surface as it provides chemical maps with high sensitivity, high mass resolution (M/∆M 10,000) and a high lateral resolution.…”

“…A three-dimensional image of the composition of film is also achieved, showing the possibilities of any diffusion across the interfaces (see Figure 2). resolution of <10 nm [67,69,[131][132][133][134][135][136][137]. For thin films, static ToF-SIMS is helpful to detect any kind of inhomogeneity and defects on the surface as it provides chemical maps with high sensitivity, high mass resolution (M/ΔM 10,000) and a high lateral resolution.…”

8. Vortices at microwave frequencies

“…In this example, we are interested mainly in an illustration of the broad features that can be observed by the study of the vortex dynamics at microwave frequencies. We consider heterostructures with an F layer (in our case, a Pd and Ni alloy of nominal composition Pd 0.84 Ni 0.16 ) of thickness d F =1, 2, 8, 9 nm, sandwiched between two superconducting Nb layers of nominal thickness d S =15 nm [42,43]. Pure Nb samples of total thickness d =20 nm and 30 nm serve as references.…”

Competitive 0 and π states in S/F/S trilayers: Multimode approach

“…For example, the critical current in S/F/S Josephson junctions exhibits a damped oscillatory behavior with increasing F layer thickness. [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43] The π state is then characterized by the negative sign of the critical current. Similarly, 0 to π transitions can also be observed in oscillations of the density of states in the F layer, [44][45][46][47] and critical temperature T c oscillations on the ferromagnetic layer thickness in S/F/S structures.…”