No abstract

Chalcogenide-based phase change materials (PCMs) are promising candidates for the active element in novel electrical nonvolatile memories and have been applied successfully in rewritable optical disks. Nanostructured PCMs are considered as the next generation building blocks for their low power consumption, high storage density, and fast switching speed. Yet their crystallization kinetics at high temperature, the rate-limiting property upon switching, faces great challenges due to the short time and length scales involved. Here we present a facile method to synthesize highly controlled, ligand-free GeTe nanoparticles, an important PCM, with an average diameter under 10 nm. Subsequent crystallization by slow and ultrafast rates allows unravelling of the crystallization kinetics, demonstrating the breakdown of Arrhenius behavior for the crystallization rate and a fragile-to-strong transition in the viscosity as well as the overall crystal growth rate for the as-deposited GeTe nanoparticles. The obtained results pave the way for further development of phase-change memory based on GeTe with sub-lithographic sizes.

The recently reported magnetic ordering in insulating two-dimensional (2D) materials, such as chromium triiodide (CrI 3 ) and chromium tribromide (CrBr 3 ), opens new possibilities for the fabrication of magnetoelectronic devices based on 2D systems. Inevitably, the magnetization and spin dynamics in 2D magnets are strongly linked to Joule heating. Therefore, understanding the coupling between spin, charge, and heat, i.e., spin caloritronic effects, is crucial. However, spin caloritronics in 2D ferromagnets remains mostly unexplored, due to their instability in air. Here we develop a fabrication method that integrates spin-active contacts with 2D magnets through hBN encapsulation, allowing us to explore the spin caloritronic effects in these materials. The angular dependence of the thermal spin signal of the CrBr 3 /Pt system is studied, for different conditions of magnetic field and heating current. We highlight the presence of a significant magnetic proximity effect from CrBr 3 on Pt revealed by an anomalous Nernst effect in Pt, and suggest the contribution of the spin Seebeck effect from CrBr 3 . These results pave the way for future magnonic devices using air-sensitive 2D magnetic insulators.

We demonstrate the potential of van der Waals magnets for spintronic applications by reporting long-distance magnon spin transport in the electrically insulating antiferromagnet chromium thiophosphate (CrPS 4 ) with perpendicular magnetic anisotropy. We inject and detect magnon spins nonlocally by Pt contacts and monitor the nonlocal resistance as a function of an in-plane magnetic field up to 7 T. We observe a nonlocal resistance over distances up to at least a micron below the Néel temperature (T N = 38 K) close to magnetic field strengths that saturate the sublattice magnetizations.

We demonstrate the potential of van der Waals magnets for spintronic applications by reporting long-distance magnon spin transport in the electrically insulating antiferromagnet chromium thiophosphate (CrPS4) with perpendicular magnetic anisotropy. We inject and detect magnon spins non-locally by Pt contacts and monitor the non-local resistance as a function of an in-plane magnetic field up to 7 Tesla. We observe a non-local resistance over distances up to at least a micron below the Neel temperature (TN = 38 Kelvin) close to magnetic field strengths that saturate the sublattice magnetizations.