We report a systematic study of the spin polarization of epitaxial ${\mathrm{CrO}}_2$ films at and across an interface using planar junctions with a superconducting counterelectrode. By chemical modification of the ${\mathrm{CrO}}_2$ surface before the deposition of the superconductor, junctions with a wide range of barrier strength were obtained. Analysis of the conductance data on these junctions, especially under Zeeman splitting of the superconducting density of states, yields consistent, close to full spin polarization for ${\mathrm{CrO}}_2$ regardless of the barrier strength.

Hydrogen sensors have been fabricated from single $\mathrm{Sn}{\mathrm{O}}_2$ nanobelts synthesized via catalyst-free thermal evaporation. Ohmic contacts were defined on individual $\mathrm{Sn}{\mathrm{O}}_2$ nanobelts by photolithography and pulsed laser deposition of $\mathrm{Ru}{\mathrm{O}}_2$ . The sensitivity and response time of the sensors, without any catalyst on the surface, to 2% hydrogen at temperatures between 25 and $80°\mathrm{C}$ were measured. Sensitivity greater than 50%, response time $<220\mathrm{s}$ , and power consumption $<10\mathrm{nW}$ at room temperature were demonstrated.

We have carried out a direct measurement of the degree of spin polarization ($\mathit{P}$) of the magnetic semiconductor ${\mathrm{G}\mathrm{a}}_{1-x}{\mathrm{M}\mathrm{n}}_x\mathrm{A}\mathrm{s}$ using Andreev reflection spectroscopy. Analyses of the conductance spectra of high transparency ${\mathrm{G}\mathrm{a}}_{0.95}{\mathrm{M}\mathrm{n}}_{0.05}\mathrm{A}\mathrm{s}/\mathrm{G}\mathrm{a}$ junctions consistently yield an intrinsic value for $\mathit{P}$ greater than 85%. Our experiments also revealed an extreme sensitivity of the measured spin polarization to the nature and quality of the interface for this material.

Chirality has been a property of central importance in physics, chemistry and biology for more than a century. Recently, electrons were found to become spin polarized after transmitting through chiral molecules, crystals, and their hybrids. This phenomenon, called chirality-induced spin selectivity (CISS), presents broad application potentials and far-reaching fundamental implications involving intricate interplays among structural chirality, topological states, and electronic spin and orbitals. However, the microscopic picture of how chiral geometry influences electronic spin remains elusive, given the negligible spin-orbit coupling (SOC) in organic molecules. In this work, we address this issue via a direct comparison of magnetoconductance (MC) measurements on magnetic semiconductor-based chiral molecular spin valves with normal metal electrodes of contrasting SOC strengths. The experiment reveals that a heavy-metal electrode provides SOC to convert the orbital polarization induced by the chiral molecular structure to spin polarization. Our results illustrate the essential role of SOC in the metal electrode for the CISS spin valve effect. A tunneling model with a magnetochiral modulation of the potential barrier is shown to quantitatively account for the unusual transport behavior.