Tunneling evidence of half-metallicity in epitaxial films of ferromagnetic perovskite manganites and ferrimagnetic magnetite

Abstract

Epitaxial diodes of a half-metallic ferromagnet on an oxide semiconductor J. Appl. Phys. 95, 7324 (2004); 10.1063/1.1669255 Enhancement of room temperature magnetoresistance in double perovskite ferrimagnets

Manifestation of the Verwey transition in the tunneling spectra of magnetite nanocrystals

“…The long-range order manifests itself by opening a gap in the electronic density of states (DOS) around the Fermi level (E F ). This gap was detected by photoemission [5,6], optical [7], and tunneling [8] spectroscopies. The effect of short-range ordering on the DOS is not as clear.…”

Spin-polarized tunneling spectroscopic studies of the intrinsic heterogeneity and pseudogap phenomena in colossal magnetoresistive manganiteLa0.7Ca0.3MnO3Hughes1, Beyer2, Yeh3 2010Phys. Rev. BSelf Cite6020View full textAdd to dashboardCite

“…Indeed, our previous optical studies of LCMO epitaxial films and single crystals [39][40][41] have revealed clear Drude-type optical conductivity below T C , implying bulk metallic behavior in the ferromagnetic state. Hence, the bulk characteristics of our LCMO samples determined from measurements of the magnetization, transport, and optical properties are all consistent with a metallic ferromagnetic phase, 21,22,35,[39][40][41] whereas manifestation of a gapped state is only found in surface sensitive measurements such as the STM and XPS studies, [17][18][19][20]35,36,42 suggesting that only the surface of LCMO is insulating. Similar results from optical measurements have also been reported for cleaved La 0.7 Sr 0.3 MnO 3 single crystals, 43 suggesting common metallic behavior in the bulk ferromagnetic phase of the manganites.…”

“…Although the occurrence of an energy gap in a nominally metallic manganite could not be explained by either band-structure calculations 10,11 or bulk electrical transport measurements, 21,22 the tunneling spectra of the metallic manganite over a wide energy range except near the Fermi level were actually consistent with theoretical calculations of the bulk electronic density of states. 17,18 Hence, it is reasonable to conjecture that the surface of manganites may be a thin layer with chemical compositions differing from those of the bulk. Thus, lower-bias ballistic electrons injected from the scanning tunneling microscopy ͑STM͒ tip could be more sensitive to the surface state, whereas ballistic electrons injected with higher bias could penetrate deeper into the bulk.…”

“…16 For instance, scanning tunneling spectroscopic ͑STS͒ studies of nominally metallic manganite epitaxial thin films [17][18][19][20] and single crystals 13 have always revealed either a small energy gap or a pseudogap ͑PG͒ near the Fermi surface. Although the occurrence of an energy gap in a nominally metallic manganite could not be explained by either band-structure calculations 10,11 or bulk electrical transport measurements, 21,22 the tunneling spectra of the metallic manganite over a wide energy range except near the Fermi level were actually consistent with theoretical calculations of the bulk electronic density of states.…”

A hybrid-exchange density functional study of Ca-doped LaMnO3

“…This is in agreement with the half-metallicity reported experimentally from scanning tunnelling spectroscopy measurements. 38 The band gap in the minority spin states is 4.57 eV. The lower valence band DOS is mainly attributed to the O 2p and Mn 3d bands, which overlap for both compositions.…”