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Abstract Unconventional spin‐orbit torques arising from electric‐field‐generated spin currents in anisotropic materials have promising potential for spintronic applications, including for perpendicular magnetic switching in high‐density memory applications. Here, all the independent elements of the spin torque conductivity tensor allowed by bulk crystal symmetries for the tetragonal conductor IrO₂are determined via measurements of conventional (in‐plane) anti‐damping torques for IrO₂thin films in the high‐symmetry (001) and (100) orientations. It is then tested whether rotational transformations of this same tensor can predict both the conventional and unconventional anti‐damping torques for IrO₂thin films in the lower‐symmetry (101), (110), and (111) orientations, finding good agreement. The results confirm that spin‐orbit torques from all these orientations are consistent with the bulk symmetries of IrO₂, and show how simple measurements of conventional torques from high‐symmetry orientations of anisotropic thin films can provide an accurate prediction of the unconventional torques from lower‐symmetry orientations. 

Abstract One of the exceptional features of the van der Waals (vdW) ferroelectrics is the existence of stable polarization at a level of atomically thin monolayers. This ability to withstand a detrimental effect of the depolarization fields gives rise to complex domain configurations characterized, among others, by the presence of layered “antipolar” head‐to‐head (H‐H) or tail‐to‐tail (T‐T) dipole arrangements. In this study, tomographic piezoresponse force microscopy (TPFM) is employed to study the 3D polarization arrangement in vdW ferroelectricα‐In₂Se₃. Sequential removal of thin layers from the polar surface using the PFM tip reveals a complex 3D profile of the domain walls in theα‐In₂Se₃crystals. Antiparallel domain layers stacked along the polar direction are also observed by PFM imaging of the non‐polar surfaces showing that H‐H and T‐T domain boundaries are commonly present inα‐In₂Se₃. Application of TPFM to the electrically written domains allows evaluation of their geometrical lateral‐to‐vertical size aspect ratio, which shows a strong prevalence for the sidewise expansion in comparison to the forward growth. LocalI–Vmeasurements reveal a strong polarization direction dependence of conductivity due to the modulation of the energy barrier height as corroborated by theoretical modeling. 

We report the experimental evidence of evolving lattice distortion in high quality epitaxial orthorhombic SrIrO3(001) thin films fully strained on (001) SrTiO3 substrates. Angle-resolved X-ray photoemission spectroscopy studies show that the surface layer of 5 nm SrIrO3 films is Sr–O terminated, and subsequent layers recover the semimetallic state, with the band structure consistent with an orthorhombic SrIrO3(001) having the lattice constant of the substrate. While there is no band folding in the experimental band structure, additional super-periodicity is evident in low energy electron diffraction measurements, suggesting the emergence of a transition layer with crystal symmetry evolving from the SrTiO3 substrate to the SrIrO3(001) surface. Our study sheds light on the misfit relaxation mechanism in epitaxial SrIrO3 thin films in the orthorhombic phase, which is metastable in bulk.