Building on earlier reports of superconductivity in bulk PtSb, we present a systematic study of superconductivity in epitaxial PtSb(0001) thin films grown on SrF 2 ( 111 ) . Electrical transport measurements reveal a superconducting transition at T c = 1.72 K . The field-induced broadening of the transition and the temperature dependence of the upper critical fields are consistent with type-II superconductivity. We determine the upper critical fields for magnetic fields applied perpendicular and parallel to the film plane and parametrize their temperature dependence using an anisotropic Ginzburg-Landau approach. For a representative film in the intermediate thickness regime ( d = 50 n m ), we obtain coherence lengths of ξ a b ≈ 56 n m and ξ c ≈ 14 n m . Current-voltage characteristics show sizable critical currents, with a critical current density reaching J c ≈ 6 × 10 4 A / cm 2 at 0.5 K . These results establish the superconducting properties of epitaxial PtSb thin films and provide a basis for lattice-matched heterostructures within the NiAs-type materials family.
We present a comprehensive study on the sputtering behavior of tungsten fuzz structures under deuterium and argon ion bombardment using three-dimensional simulations. We employed SDTrimSP-3D to investigate porosity as a predictor for the sputtering behavior, complementary to the well-established effects of surface roughness, with simulations conducted across multiple ion energies ( 500 eV – 2000 eV ) and incidence angles ( 0 ∘ − 85 ∘ ). Fuzz structures were algorithmically generated with varying porosities, and sputter yields were systematically calculated. The findings reveal a universal linear relationship between sputter yield and porosity/volume filling, demonstrating that porosity significantly suppresses sputtering. Importantly, the zero-porosity limit is given by the sputter yield of a rough, but solid surface rather than a flat target. This linear behavior holds consistently across the different ion types and energies for a wide range of incidence angles. When normalized to the rough-surface sputter yield, the slope of the porosity dependence is nearly constant, indicating a common underlying suppression mechanism. The study enhances fundamental understanding of sputtering in porous nanostructures and provides a simple, predictive framework with implications for material design, particularly in nuclear fusion research, where erosion of tungsten fuzz impacts reactor component lifetimes.
Sr 2 IrO 4 (Sr214) and related iridates have emerged as key platforms for fundamental correlated-electron physics and for potential applications such as magnonics. Here, we report the epitaxial growth of high-quality Sr214 thin films using reactive off-axis sputtering. Conventional pulsed-laser deposition of Sr214 suffers from limitations arising from the volatility and decomposition of iridates, which often result in parasitic Ruddlesden–Popper phases and iridium vacancies. By employing sputtering, we mitigate these issues and achieve stable growth conditions that allow precise mapping of the phase diagram. Systematic variation of the growth temperature reveals that Sr214 stabilizes within a window between 825 ∘ C and 1050 ∘ C , with optimal crystallinity and thickness obtained at 840 ∘ C . Raman spectroscopy provides sensitive diagnostics of iridium vacancies, with defect-induced phonon modes and peak intensity ratios correlating strongly with the c -axis lattice parameter. Our results establish reactive sputtering as a robust route for integrating Sr214 into oxide electronic and magnonic device architectures.
The magnetic damping of spin-pumping heterostructures consisting of Pt and Ni 80 Fe 20 (Permalloy, Py) thin films is studied via temperature- and frequency-dependent ferromagnetic resonance (FMR). Additional magnetic and structural characterization is done by transmission electron microscopy (TEM), x-ray absorption spectroscopy, and x-ray magnetic circular dichroism (XMCD). The frequency-dependence of the FMR linewidth allows to extract the Gilbert damping parameter α as a function of temperature. Py in direct contact with Pt exhibits a strong enhancement of α ( T ) , and the dependence on the thickness of the Py layer suggests this to be an interfacial effect. The enhanced α ( T ) is accompanied by an induced magnetic polarization of the Pt as evidenced by XMCD, while the other magnetic properties of Py as measured with FMR and static magnetometry remain virtually unchanged. The increase of α ( T ) can be efficiently suppressed by the insertion of an Al-spacer layer between Pt and Py as thin as 1 nm, which coincides with the loss of the magnetic polarization of Pt.
We report the evolution of the antiferromagnetic domain structure of epitaxial La 0.45 Sr 0.55 MnO 3 (LSMO) ultrathin films with thickness in the range from 5–50 unit cells (uc), using x-ray photoemission electron microscopy (XPEEM). While the 5 uc thick LSMO shows no magnetic contrast down to ∼ 80 K , thicker films display a multidomain antiferromagnetic configuration with a nonmonotonic variation in the characteristic domain size from 0.3 µ m at 10 uc, to 3–5 µ m at 15–16 uc and 1 µ m for 50 uc. Post-growth annealing is found not to impact strongly the magnetic domain state. In contrast, for a 15 uc film grown on a substrate characterized by large atomic steps ( ∼ 1 µ m ) , we observe much larger antiferromagnetic domains and the presence of net magnetic moment in the form of stripes with alternating contrast, assigned to the signal from the top uncompensated spins of the A-type antiferromagnetic state of LSMO. From the combined antiferromagnetic domain structure and the net magnetic moment contrast, we determine the exact orientation of the Néel vector, including at domain walls. We describe the antiferromagnetic domain size distribution in terms of interface and bulk contributions to the density of defects that pin the antiferromagnetic domain walls and which determine the equilibrium domain configuration. Our results demonstrate the impact of thickness and defects on the antiferromagnetic domain size and constitute a stepping stone in controlling the antiferromagnetic domain state required for oxide antiferromagnetic device applications.
Dislocation climb is one of the key processes controlling the mechanical response and microstructure evolution of materials at high temperatures. The mechanisms of this phenomenon are still unclear due to its complex nature, which involves interactions between point defects and dislocations. Here we employed large-scale classical molecular-dynamics (MD) simulations to shed light on vacancy-driven dislocation climb in fcc Ni. A Ni crystal with dissociated dislocations was simulated under high-temperature vacancy supersaturation for multiple nanoseconds. A particular advantage of this method is the ability to reveal the underlying mechanisms of dislocation climb without prior knowledge. The study included three different dislocation characters: pure edge, mixed 30 ∘ , and 60 ∘ . We found that jog-pair formation initiated with vacancy clustering at partial dislocations, followed by the alignment of vacancies into linear clusters along the 〈 110 〉 direction. This stage was clarified by a detailed analysis of vacancy segregation energies at dissociated dislocations for vacancy clusters of different sizes and configurations. Subsequent stages of jog-pair formation involved local reduction of the stacking-fault region and further jog-pair growth due to vacancy accumulation. From the MD simulations, we traced the full dislocation climb process and compared it with classical descriptions of dislocation climb in fcc metals. Detailed analysis of the MD results allowed us to resolve and describe all stages of dislocation climb from the perspective of dislocation reactions. Based on the changes in dislocation positions, we estimated the climb velocity for the considered dislocations driven by the osmotic force.
Topological properties and topological superconductivity in real materials have attracted intensive experimental and theoretical attentions recently. The topological electronic properties of pressure-induced superconductors BiH2 have been studied based on first-principles electronic structure calculations. Recent experiments have revealed that BiH2 exhibits five distinct phases under high pressure, our studies show that Cmcm-BiH2, Pnma-BiH2, Pnnm-BiH2, and P21/m-BiH2 are all topological metals defined on curved Fermi levels, while the P212121-BiH2 holds Weyl points near the Fermi level. The topological surface states (TSSs) and Fermi arcs of BiH2 right cross the Fermi level and hold helical spin textures. Considering the fact that the BiH2 exhibit high superconducting transition temperatures (Tc) of similar to 70 K under pressure confirmed by recent experiments, the superconducting bulks will induce superconductivity in the TSSs via the proximity effect. Thus, the hydride superconductors BiH2 may provide a promising platform for exploring topological superconductivity and Majorana zero modes.
Electrical switching of antiferromagnets (AFM) is critical for AFM spintronics. However, electrical pulse-induced N & eacute;el vector reorientation in AFM insulators, while predicted to occur at much faster timescales than ferromagnetic switching, has only been demonstrated in the quasi-DC regime. Here we report reliable current-induced AFM switching in Pt/alpha-Fe2O3 bilayers using electrical pulses with various durations spanning three orders of magnitude down to 0.3 ns. Together with COMSOL simulations of temperature distributions in our samples for various pulse widths, our results suggest that thermally assisted spin-orbit torque likely play an important role for sub-ns pulses. This work demonstrates the viability of electrical switching of AFM spins using sub-ns pulses.
