Absolute crystal and magnetic chiralities in the langasite compound Ba3NbFe3Si2O14 determined by polarized neutron and x-ray scattering
Physical Review B American Physical Society 102:5 (2020) 54417
Abstract:
We present a combined polarized neutron and x-ray scattering study on two enantiopure langasite single crystals aimed at the determination of their absolute structural and magnetic chiralities and the coupling between them. Our respective data sets unambiguously reveal two samples of opposite structural chirality, where the magnetic handedness is pinned by the structural one. Simple energy considerations of the magnetic exchange and single-ion anisotropy parameters reveal that it is not the Dzyaloshinskii-Moriya interaction but the local single-ion anisotropy on a triangular plaquette which plays a key role in stabilizing one of the two magnetic helices.Emergent helical texture of electric dipoles
Science American Association for the Advancement of Science 369:6504 (2020) 680-684
Micromagnetic modelling and imaging of vortex/merons structures in an oxide | metal heterostructure
Physical Review B American Physical Society 101:14 (2020) 144420
Abstract:
Using micromagnetic simulations, we have modelled the formation of imprinted merons and anti-merons in cobalt overlayers of different thickness (1-8 nm), stabilised by interfacial exchange with antiferromagnetic vortices in $\alpha$-Fe2O3. Structures similar to those observed experimentally could be obtained with reasonable exchange parameters, also in the presence of surface roughness. We produce simulated meron/antimeron images by magnetic force microscopy (MFM) and nitrogen-vacancy (N-V) centre microscopy, and established signatures of these topological structures in different experimental configurations.Magneto-optical Kerr switching properties of (CrI3)2 and (CrBr3/CrI3) bilayers
ACS Applied Electronic Materials American Chemical Society 2:5 (2020) 1373-1380
Abstract:
We explore the magneto-optical Kerr effect (MOKE) for different spin configurations of the (CrI3)2 bilayer and (CrBr3/CrI3) mixed bilayer using symmetry arguments and first-principles electronic structure calculations. Starting from CrX3 (X = I, Br) monolayers, we considered collinear ferromagnetic (FM) and layered antiferromagnetic (AFM) states for (CrI3)2 and (CrBr3/CrI3) bilayers. The AFM (CrI3)2 bilayer does not show MOKE, consistent with the presence of a symmetry operator combining inversion (I) and time reversal (T) symmetries. The FM state preserves I symmetry but breaks the T symmetry, thus allowing a nonzero Kerr angle, which is reversible by switching the FM spins. The (CrBr3/CrI3) bilayer breaks both the I and T symmetries and thus exhibits MOKE both in the FM state and, remarkably, in the AFM state. In both FM and AFM configurations, the Kerr angle switches by reversing the spins in both layers. Our study demonstrates that the MOKE spectra can help to characterize different magnetic configurations in these emerging two-dimensional (2D) magnetic materials due to a different stacking of the monolayers, even in the AFM case. Note that the present symmetry analyses and MOKE properties apply to more general 2D magnetic van der Waals heterostructures. Furthermore, we propose the (CrBr3/CrI3) bilayer as a promising candidate for AFM spintronics since the two time-reversed AFM states are associated with opposite Kerr rotation, i.e., they could be used as memory elements.Spin-wave directional anisotropies in antiferromagnetic Ba3NbFe3Si2O14
Physical Review B American Physical Society 100:13 (2019) 134429