In a prototypical ferromagnet (Ga,mn)As based on a III-V semiconductor, substitution of divalent mn atoms into trivalent Ga sites leads to severely limited chemical solubility and metastable specimens available only as thin films. The doping of hole carriers via (Ga,mn) substitution also prohibits electron doping. To overcome these difficulties, masek et al. theoretically proposed systems based on a I-II-V semiconductor LiZnAs, where isovalent (Zn,mn) substitution is decoupled from carrier doping with excess/deficient Li concentrations. Here we show successful synthesis of Li 1 + y (Zn 1 − x mn x )As in bulk materials. Ferromagnetism with a critical temperature of up to 50 K is observed in nominally Li-excess (y = 0.05-0.2) compounds with mn concentrations of x = 0.02-0.15, which have p-type metallic carriers. This is presumably due to excess Li in substitutional Zn sites. semiconducting LiZnAs, ferromagnetic Li(Zn,mn)As, antiferromagnetic LimnAs, and superconducting LiFeAs systems share square lattice As layers, which may enable development of novel junction devices in the future.
The observation of a high-mobility two-dimensional electron gas between two insulating complex oxides, especially LaAlO3/SrTiO3, has enhanced the potential of oxides for electronics. The occurrence of this conductivity is believed to be driven by polarization discontinuity, leading to an electronic reconstruction. In this scenario, the crystal orientation has an important role and no conductivity would be expected, for example, for the interface between LaAlO3 and (110)-oriented SrTiO3, which should not have a polarization discontinuity. Here we report the observation of unexpected conductivity at the LaAlO3/SrTiO3 interface prepared on (110)-oriented SrTiO3, with a LaAlO3-layer thickness-dependent metal-insulator transition. Density functional theory calculation reveals that electronic reconstruction, and thus conductivity, is still possible at this (110) interface by considering the energetically favourable (110) interface structure, that is, buckled TiO2/LaO, in which the polarization discontinuity is still present. The conductivity was further found to be strongly anisotropic along the different crystallographic directions with potential for anisotropic superconductivity and magnetism, leading to possible new physics and applications.
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