Crystal growth and metallic ferromagnetism induced by electron doping in FeSb2

Abstract

In order to study the metallic ferromagnetism induced by electron doping in the narrow-gab semiconductor FeSb2, single crystals of FeSb2, Fe1-xCoxSb2 (0 x 0.5) and FeSb2-yTey (0 y 0.4), were grown by a simplified self-flux method. From powder x-ray diffraction (XRD) patterns, wavelength-dispersive x-ray spectroscopy (WDX) and x-ray Laue diffraction, pure and doped high-quality single crystals, within the selected solubility range, show only the orthorhombic Pnnm structure of FeSb2 with a monotonic change in lattice parameters with increasing the doping level. In consistence with the model of nearly ferromagnetic small-gap semiconductor, the energy gap of FeSb2 Pauli paramagnet gradually collapses by electron doping before it closes at about x or y = 0.15 and subsequent itinerant electron anisotropic ferromagnetic states are observed with higher doping levels. A magnetic phase diagram is established and discussed in view of proposed theoretical scenarios.