Exchange interaction and its tuning in magnetic binary chalcogenides

Using a first-principles Green's function approach we study magnetic properties of the magnetic binary chalcogenides Bi2Te3, Bi2Se3, and Sb2Te3. The magnetic coupling between transition-metal impurities is long-range, extends beyond a quintuple layer, and decreases with increasing number of d electrons per 3d atom. We find two main mechanisms for the magnetic interaction in these materials: the indirect exchange interaction mediated by free carriers and the indirect interaction between magnetic moments via chalcogen atoms. The calculated Curie temperatures of these systems are in good agreement with available experimental data. Our results provide deep insight into magnetic interactions in magnetic binary chalcogenides and open a way to design new materials for promising applications

Ab initio design of quaternary Heusler compounds for reconfigurable magnetic tunnel diodes and transistors

Reconfigurable magnetic tunnel diodes and transistors are a new concept in spintronics. The realization of such a device requires the use of materials with unique spin-dependent electronic properties such as half-metallic magnets (HMMs) and spin-gapless semiconductors (SGSs). Quaternary Heusler compounds offer a unique platform to design within the same family of compounds HMMs and SGSs with similar lattice constants to make coherent growth of the consecutive spacers of the device possible. Employing state-of-the-art first-principles calculations, we scan the quaternary Heusler compounds and identify suitable candidates for these spintronic devices combining the desirable properties: (i) HMMs with sizable energy gap or SGSs with spin gaps both below and above the Fermi level, (ii) high Curie temperature, (iii) convex hull energy distance less than 0.20 eV, and (iv) negative formation energies. Our results pave the way for the experimental realization of the proposed magnetic tunnel diodes and transistors.Comment: 13 pages, 9 figure

Gate-tuneable and chirality-dependent charge-to-spin conversion in tellurium nanowires

Chiral materials are an ideal playground for exploring the relation between symmetry, relativistic effects and electronic transport. For instance, chiral organic molecules have been intensively studied to electrically generate spin-polarized currents in the last decade, but their poor electronic conductivity limits their potential for applications. Conversely, chiral inorganic materials such as tellurium have excellent electrical conductivity, but their potential for enabling the electrical control of spin polarization in devices remains unclear. Here, we demonstrate the all-electrical generation, manipulation and detection of spin polarization in chiral single-crystalline tellurium nanowires. By recording a large (up to 7%) and chirality-dependent unidirectional magnetoresistance, we show that the orientation of the electrically generated spin polarization is determined by the nanowire handedness and uniquely follows the current direction, while its magnitude can be manipulated by an electrostatic gate. Our results pave the way for the development of magnet-free chirality-based spintronic devices.This work is supported by the Spanish Ministerio de Ciencia e Innovación (MICINN) under projects RTI2018-094861-B-100 and PID2019-108153GA-I00 and under the Maria de Maeztu Units of Excellence Programme (MDM-2016-0618); by the European Union Horizon 2020 under the Marie Slodowska-Curie Actions (0766025-QuESTech and 892983-SPECTER); and by Intel Corporation under ‘FEINMAN’ and ‘VALLEYTRONICS’ Intel Science Technology Centers. B.M.-G. acknowledges support from the Gipuzkoa Council (Spain) in the frame of the Gipuzkoa Fellows Program. M.S.-R. acknowledges support from La Caixa Foundation (no. 100010434) with code LCF/BQ/DR21/11880030. M.G. acknowledges support from La Caixa Foundation (no. 100010434) for a Junior Leader fellowship (grant no. LCF/BQ/PI19/11690017). A.J. acknowledges support from CRC/TRR 227 of Deutsche Forschungsgemeinschaft.Peer reviewe