11 research outputs found
Spin-valve nature and giant coercivity of a ferrimagnetic spin semimetal MnIrGa
Spin semimetals are amongst the most recently discovered new class of
spintronic materials, which exhibit a band gap in one spin channel and
semimetallic feature in the other, thus facilitating tunable spin transport.
Here, we report MnIrGa to be a candidate material for spin semimetal along
with giant coercivity and spin-valve characteristics using a combined
experimental and theoretical study. The alloy crystallizes in an inverse
Heusler structure (without any martensitic transition) with a para- to
ferri-magnetic transition at 243 K. It shows a giant
coercive field of about 8.5 kOe (at 2 K). The negative temperature coefficient,
relatively low magnitude and weak temperture dependance of electrical
resistivity suggest the semimetallic character of the alloy. This is further
supported by our specific heat measurement. Magnetoresistance (MR) confirms an
irreversible nature (with its magnitude 1\%) along with a change of sign
across the magnetic transition indicating the potentiality of MnIrGa in
magnetic switching applications. In addition, asymmetric nature of MR in the
positive and negative field cycles is indicative of spin-valve characteristics.
Our ab-initio calculations confirm the inverse Heusler structure with
ferrimagnetic ordering to be the lowest energy state, with a saturation
magnetization of 2 . is found to be the easy magnetic
axis with considerable magneto-crystalline anisotropy energy. A large positive
Berry flux at/around point gives rise to an appreciable anomalous Hall
conductivity (-180 S/cm).Comment: Mn2IrGa, Inverse Heusler alloys, Giant Coercivity, Ferrimagnets, Spin
Semimetal, Spin valve, Fleur, FLAPW, Spintronic
Multiple Dirac cones at the surface of the topological metal LaBi
The rare-earth monopnictide LaBi exhibits exotic magneto-transport properties, including an extremely large and anisotropic magnetoresistance. Experimental evidence for topological surface states is still missing although band inversions have been postulated to induce a topological phase in LaBi. In this work, we have revealed the existence of surface states of LaBi through the observation of three Dirac cones: two coexist at the corners and one appears at the centre of the Brillouin zone, by employing angle-resolved photoemission spectroscopy in conjunction with ab initio calculations. The odd number of surface Dirac cones is a direct consequence of the odd number of band inversions in the bulk band structure, thereby proving that LaBi is a topological, compensated semimetal, which is equivalent to a time-reversal invariant topological insulator. Our findings provide insight into the topological surface states of LaBi’s semi-metallicity and related magneto-transport properties
Electronic structure of the unoccupied electron energy states in FeSe1-xTex
Inverse photoemission spectroscopic (IPES) measurements along with LDA based band structure calculations have been used to investigate the unoccupied electronic structure of FeSe1-xTex system. The observed doping and temperature dependent pseudogap in this system is found to be linked to the change in the chalcogen height in their geometric structure. The depletion in spectral weight from the near E-F states at low temperature in IPES has been correlated with the enhancement of the 3z(2)-r(2) orbitals in the photoemission spectroscopy (PES). The Coulomb correlation energy U, estimated from the combined PES and IPES spectra, signifies the enhancement in electron correlations in FeSe1-xTex, with doping. The formation of pseudogap in PES and IPES confirms the importance of correlations in the 11 family of Fe superconductors
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Signatures of Sixfold Degenerate Exotic Fermions in a Superconducting Metal PdSb2
Multifold degenerate points in the electronic structure of metals lead to exotic behaviors. These range from twofold and fourfold degenerate Weyl and Dirac points, respectively, to sixfold and eightfold degenerate points that are predicted to give rise, under modest magnetic fields or strain, to topological semimetallic behaviors. The present study shows that the nonsymmorphic compound PdSb2 hosts six-component fermions or sextuplets. Using angle-resolved photoemission spectroscopy, crossing points formed by three twofold degenerate parabolic bands are directly observed at the corner of the Brillouin zone. The group theory analysis proves that under weak spin–orbit interaction, a band inversion occurs. © 2020 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinhei