(LaCrO3)m/SrCrO3 superlattices as transparent p-type semiconductors with finite magnetization

The electronic and magnetic properties of (LaCrO3)m/SrCrO3 superlattices are investigated using first principles calculations. We show that the magnetic moments in the two CrO2 layers sandwiching the SrO layer compensate each other for even m but give rise to a finite magnetization for odd m, which is explained by charge ordering with Cr3+ and Cr4+ ions arranged in a checkerboard pattern. The Cr4+ ions induce in-gap hole states at the interface, implying that the transparent superlattices are p-type semiconductors. The availability of transparent p-type semiconductors with finite magnetization enables the fabrication of transparent magnetic diodes and transistors, for example, with a multitude of potential technological applications

Ferromagnetism and ferroelectricity in a superlattice of antiferromagnetic perovskite oxides without ferroelectric polarization

Abstract We study the structural, electronic, and magnetic properties of the SrCrO3/YCrO3 superlattice and their dependence on epitaxial strain. We discover that the superlattice adopts A-type antiferromagnetic (A-AFM) ordering in contrast to its constituents (SrCrO3: C-AFM; YCrO3: G-AFM) and retains it under compressive strain while becoming ferromagnetic (5 μ B per formula unit) at +1% strain. The obtained ferroelectric polarization is significantly higher than that of the R2NiMnO6/La2NiMnO6 (R = Ce to Er) series of superlattices [Nat. Commun. 5, 4021 (2014)] due to a large difference between the antipolar displacements of the Sr and Y cations. The superlattice is a hybrid-improper multiferroic material with a spontaneous ferroelectric polarization (13.5 μC/cm2) approaching that of bulk BaTiO3 (19 μC/cm2). The combination of ferromagnetism with ferroelectricity enables multistate memory applications. In addition, the charge-order-driven p-type semiconducting state of the ferromagnetic phase (despite the metallic nature of SrCrO3) is a rare property and interesting for spintronics. Monte Carlo simulations demonstrate a magnetic critical temperature of 90 K for the A-AFM phase without strain and of 115 K for the ferromagnetic phase at +5% strain, for example

Studies toward the total synthesis of Cytospolide E

In this manuscript, we describe various approaches that we have examined towards the total synthesis of Cytospolide E. We initially attempted the RCM approach employing first and second generation Grubbs and Grubbs–Hoyeda catalysts resulting in the exclusive synthesis of the Z-isomer of Cytospolide E. With the Fürstner catalyst, the dimerization involving the less hindered olefin was the exclusive event. Alternative approach documented is a successful cross-metathesis leading to a seco-acid with the requisite E-configuration and undesired macrodiolide formation during the attempted Shiina's lactonization