4 research outputs found
Polar magneto-optical Kerr effect in antiferromagnetic MAs (M=Cr, Mn, Fe) under an external magnetic field
Antiferromagnetic metals attract tremendous interest for memory applications
due to their expected fast response dynamics in the terahertz frequency regime.
Reading from and writing information into these materials is not easily
achievable using magnetic fields, due to weak high-order magneto-optical
signals and robustness of the magnetic structure against external magnetic
fields. Polarized electromagnetic radiation is a promising alternative for
probing their response, however, when ideal antiferromagnetic symmetry is
present, this response vanishes. Hence, in this work we combine
first-principles simulations with measurements of the polar magneto-optical
Kerr effect under external magnetic fields, to study magneto-optical response
of antiferromagnetic MAs (M=Cr, Mn, and Fe). We devise a computational
scheme to compute the magnetic susceptibility from total-energy changes using
constraints on magnetic-moment tilting. Our predictions of the spectral
dependence of polar magneto-optical Kerr rotation and ellipticity allow us to
attribute these effects to breaking of the magnetic symmetry. We show that
tilting affects the exchange interaction, while the spin-orbit interaction
remains unaffected as the tilting angle changes. Our work provides
understanding of the polar magneto-optical Kerr effect on a band structure
level and underscores the importance of the magnetic susceptibility when
searching for materials with large magneto-optical response.Comment: 9 pages, 9 figure
Wideband luminescence from bandgap-matched Mg-based Si core-shell geometry nanocomposite
We use wet treatment to integrate red-luminescent Si nanoparticles with Mg-based wide-bandgap insulators Mg(OH) and MgO (5.7 and 7.3 eV respectively). In the process, Mg2+ is reduced on Si nanoparticle clusters, while suffering combustion in water, producing a spatially inhomogeneous Mg(OH)2/MgO-Si nanoparticle composite with an inner material predominantly made of Si, and a coating consisting predominantly of magnesium and oxygen (“core-shell” geometry). The nanocomposite exhibit luminescence covering nearly entire visible range. Results are consistent with formation of Mg(OH)2/MgO phase with direct 3.43-eV bandgap matching that of Si, with in-gap blue-green emitting states of charged Mg and O vacancies. Bandgap match with nanocomposite architecture affords strong enough coupling for the materials to nearly act as a single hybrid material with novel luminescence for photonic and photovoltaic applications