We discover that large uniaxial magnetocrystalline anisotropy driven by the simultaneous presence of spin–orbit coupling and structural distortions is the origin of the giant coercivity observed experimentally in the double perovskite Lu2NiIrO6. The magnetic easy axis turns out to be the monoclinic b-axis with an anisotropy constant as high as 1.9 × 108 erg/cm3. The predicted coercive field of 50 kOe and Curie temperature of 220 K agree with the experimentally observed values and point to potential of Lu2NiIrO6 in spintronics applications. We find that the spin–orbit coupling induces a rare Ir4+ J eff = 1/2 Mott insulating state, suggesting that Lu2NiIrO6 provides a playground to study the interplay between spin–orbit coupling and electronic correlations in a 5d transition metal oxide. The spin–orbit coupling also results in a direct band gap with the valence and conduction states localized on different transition metal sublattices, i.e., efficient electron–hole separation upon photoexcitation and low electron–hole recombination.

We have investigated the effect of epitaxial strain on the magnetic properties and B-site cation ordering in multiferroic Bi2FeCrO6 (001) thin films using a density-functional theory approach. We find that in thin films with rock-salt ordering of Fe and Cr the ground state is characterised by C-type anti-ferromagnetic (AFM) order. This is in contrast to the bulk form of the material which was predicted to be a ferrimagnet with Gtype AFM order. Furthermore, the cation ordered thin-films undergo a transition with epitaxial strain from C to A-type AFM order. Other magnetic orders appear as thermally accessible excited states. We also find that B-site cation disordered structures are more stable in coherent epitaxial strains thereby explaining the lowered magnetic moments observed in these samples at room temperature. Strain varies both the sign as well as strength of the Fe-Cr superexchange coupling resulting in a very interesting phase diagram for Bi2FeCrO6 thin films.

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Perovskite metal-organic frameworks (MOFs) have recently emerged as potential candidates for multiferroicity. However, the compounds synthesized so far possess only weak ferromagnetism and low polarization. Additionally, the very low magnetic transition temperatures (Tc) also pose a challenge to the application of the materials.We have computationally designed a mixed metal perovskite MOF -[C(NH2)3][(Cu0.5Mn0.5)(HCOO)3]-that is predicted to have magnetization two orders of magnitude larger than its parent ([C(NH2)3][Cu(HCOO)3]), a significantly larger polarization (9.9 µC/cm 2 ), and an enhanced Tc of up to 56 K, unprecedented in perovskite MOFs. A detailed study of the magnetic interactions revealed a novel mechanism leading to the large moments as well as the increase in the Tc. Mixing a non-Jahn-Teller ion (Mn 2+ ) into a Jahn-Teller host (Cu 2+ ) leads to competing lattice distortions which are directly responsible for the enhanced polarization. The MOF is thermodynamically stable as evidenced by the computed enthalpy of formation, and can likely be synthesized. Our work represents a first step towards rational design of multiferroic perovskite MOFs through the largely unexlpored mixed metal approach.Multiferroics are materials which possess ferromagnetic (FM), ferroelectric (FE) and structural order parameters within a single phase [1][2][3][4][5][6][7][8]. These are highly promising not only for their use in multi-functional device applications but also for the interesting physics they reveal. Much of the research in the field has so far focussed on multiferroics based on inorganic transition metal oxides. In the last decade, there has been growing interest in metal-organic frameworks (MOFs) consisting of metal ions interconnected by organic linkers. The organic-inorganic duality in MOFs leads to many interesting physical properties [9,10] that can be exploited in applications such as gas storage and separation, catalysis, nonlinear optics, photoluminescence, magnetic and electric materials, and so on [11,12]. The hybrid nature of these materials offers a vast chemical space for synthetic chemists to explore and, hence, also affords tunability of properties. MOFs with the perovskite ABX 3 structure are of great interest, particularly those with multiferroic behavior arising due to hydrogen-bonds [13,14]. In the case of magnetic MOFs, for instance, one can control the nature of magnetic coupling through the variety of possible metal ions in the B-site, short ligands, co-ligands and radical ligands carrying spin degrees of freedom [15]. Recently, it has been shown that one can tune the magnitude of the ferroelectric polarization by carefully choosing different A-site cations in these MOFs [16].In recent past, a new class of ABX 3 metal formates [C(NH 2 ) 3 ][M(HCOO) 3 ] (abbreviated below as M-MOF, M= divalent Mn, Fe, Co, Ni, Cu, and Zn), was experimentally synthesized [17]. Of these only the Cu-MOF crystallizes into a polar space group (Pna2 1 ) and exhibits multiferroic and magnetoelectric behavior. It has...

Two-dimensional semiconductors have great potential in high-performance electronic devices. However, the common way of contacting them with metals to inject charge carriers results in contact resistance. We propose a junction-free field-effect transistor consisting of semiconducting monolayer blue phosphorene as channel material (with high carrier mobility) and metallic bilayer blue phosphorene as electrodes. The junction-free design minimizes the contact resistance. Employing first-principles calculations along with the non-equilibrium Green’s function method, we demonstrate a high Ion/Ioff ratio of up to 2.6 × 104 and a remarkable transconductance of up to 811 μS/μm.