Electron spectroscopy study of single-crystal CrTe

We study characterized single crystals of CrTe using photoemission spectroscopy (PES), x-ray absorption spectroscopy (XAS), and x-ray magnetic circular dichroism (XMCD) combined with density functional theory--based electronic structure calculations. X-ray diffraction confirms the hexagonal structure of CrTe ($P63/mmc$ space group) and $T$-dependent magnetization $M(T)$ shows a Curie temperature ${T}_{C}=340\phantom{\rule{0.28em}{0ex}}\mathrm{K}$, with a three-dimensional Ising-type critical behavior. A quantitative analysis of $\mathrm{Cr}\phantom{\rule{0.28em}{0ex}}3p$ and $\mathrm{Te}\phantom{\rule{0.28em}{0ex}}4d$ core levels using hard x-ray PES (HAXPES; $h\ensuremath{\nu}=6.5\phantom{\rule{0.28em}{0ex}}\mathrm{keV}$) and low-energy PES $(h\ensuremath{\nu}=100\phantom{\rule{0.28em}{0ex}}\mathrm{eV})$ indicates a nearly stoichiometric composition of ${\mathrm{Cr}}_{0.99\ifmmode\pm\else\textpm\fi{}0.01}\mathrm{Te}$. HAXPES of $\mathrm{Te}\phantom{\rule{0.28em}{0ex}}3p$ and $3d$ core levels show clean asymmetric single peaks with plasmon satellites. The $\mathrm{Cr}\phantom{\rule{0.28em}{0ex}}2p$ spectrum lies close to the $\mathrm{Te}\phantom{\rule{0.28em}{0ex}}3d$ spectrum but could be separated out and shows weak charge-transfer satellites. The Cr $L$-edge XAS-XMCD and $\mathrm{Cr}\phantom{\rule{0.28em}{0ex}}2p$ PES spectra could be simulated using charge transfer multiplet cluster-model calculations for a ${\mathrm{Cr}}^{2+}$ configuration with on-site Coulomb energy ${U}_{dd}=3.5\phantom{\rule{0.28em}{0ex}}\mathrm{eV}$ and a negative charge-transfer energy $\mathrm{\ensuremath{\Delta}}=\ensuremath{-}1\phantom{\rule{0.28em}{0ex}}\mathrm{eV}$. A sum-rule analysis of XAS-XMCD spectra indicates a very small orbital magnetic moment ${m}_{o}=0.01\ifmmode\pm\else\textpm\fi{}0.01\phantom{\rule{0.28em}{0ex}}{\ensuremath{\mu}}_{B}$ and a spin magnetic moment ${m}_{s}=2.49\ifmmode\pm\else\textpm\fi{}0.2\phantom{\rule{0.28em}{0ex}}{\ensuremath{\mu}}_{B}$ at $T=25\phantom{\rule{0.28em}{0ex}}\mathrm{K}$, consistent with magnetization measurements and cluster-model calculations. Comparison of the calculated density of states (DOS) with the HAXPES valence band spectrum shows that the $\mathrm{Te}\phantom{\rule{0.28em}{0ex}}5p$ states dominates the spectrum due to the large photoionization cross section of Te $5p$ states with hard x rays. The Cr $3d$ partial DOS are spread between the Fermi level $({E}_{F}$) to $\ensuremath{\sim}5\text{\ensuremath{-}}\mathrm{eV}$ binding energy (BE), while the $\mathrm{Te}\phantom{\rule{0.28em}{0ex}}5p$ partial DOS are spread between the ${E}_{F}$ and $\ensuremath{\sim}7\text{\ensuremath{-}}\mathrm{eV}$ BE. The obtained electronic parameters suggest that CrTe is a $p$-type metal in the Zaanen-Sawatzky-Allen phase diagram, with $p\ensuremath{\rightarrow}p$-type lowest-energy excitations.