Tunneling spectroscopy on the correlation effects in FeSi

Abstract

We have performed electron tunneling spectroscopy on FeSi single crystals in the temperature range 4-300 K by using a scanning tunneling microscope. The differential conductance (dI/dV), when corrected for Schottky barrier effects, exhibits two strongly temperature-dependent peaks on either side of the Fermi level that emerge below Ϸ200 K and that are separated by a ͑pseudo͒gap of Ϸ50 meV. Our observations can be ascribed to the formation of quasiparticle density of states caused by d-electron correlation. The tunneling spectra are in good agreement with photoemission spectroscopy as both techniques probe the correlated d-electron density of states ͑DOS͒. Our results are also consistent with optical reflectivity data and Raman spectroscopy, which, in contrast, are sensitive to the conduction (c) electron DOS. ͓S0163-1829͑98͒08248-4͔

Magnetodielectric consequences of phase separation in the colossal magnetoresistance manganitePr0.7Ca0.3MnO3

“…This is very interesting, since it implies that the first order insulator-metal transition which is observed near 4 tesla can be attributed to a suppression of the polaron hopping energy barrier. The nature of this transition (which is from a nearly ferromagnetic state to a fully ferromagnetic state) has been the subject of considerable interest, ,30 and our data indicate it to be associated with field-induced effects on correlated electronic behavior in the charge-ordered antiferromagnetic portion of the sample rather than through percolation of a ferromagnetic metallic phase (as has been convincingly demonstrated in other phase-separated materials 31,32 ). The non-percolative nature of the field-induced phase transition is consistent with previous studies on the Pr 0.7 Ca 0.3 MnO 3 system that demonstrate the transition is strongly first order.…”

Effect of disorder in an orbitally ordered Jahn-Teller insulator

“…Quenched disorder has been widely acknowledged as a crucial ingredient for the understanding of hole-doped manganites [3,4]. It is the source of a variety of phenomena, both in real materials as well as in model calculations, like the coexistence of metallic and insulating phases [5,6,7,8,9], thermally driven metal to insulator transitions [10,11,12,13], and the suppression of charge order in half-doped systems [14,15].…”

Giant and reversible extrinsic magnetocaloric effects in La0.7Ca0.3MnO3 films due to strain

“…(Table 1). By exploiting a first-order structural phase transition in BaTiO 3 (BTO) substrates, we create giant and reversible MC effects in epitaxial films of LCMO via the entropic interconversion of ferromagnetic and paramagnetic phases, whose coexistence 17,18 we reveal using photoemission electron microscopy (with magnetic contrast from x-ray magnetic circular dichroism) and ferromagnetic resonance.These extrinsic MC effects arise due to a strain-mediated feedback mechanism near the rhombohedral-orthorhombic transition in BTO at ~200 K, i.e. well away from LCMO C T at which the small intrinsic MC effects are seen.…”

“…Of critical importance here, the high-field high-magnetization state ( high-magnetization state must also be reversible 17 .) If the non-interfacial BTO were absent, we anticipate that magnetically driving the jump in the thermally hysteretic regime would be irreversible, cf.…”