Vacancy-induced pseudo-gap formation in antiferromagnetic Cr$_{0.86}$ZnSb

Structural defects are important for both solid-state chemistry and physics, as they can have a significant impact on chemical stability and physical properties. Here, we identify a vacancyinduced pseudo-gap formation in antiferromagnetic Cr$_{0.86}$ZnSb. Cr$_{1-x}$ZnSb alloys were studied combining efforts of density functional theory (DFT) calculations and experimental methods to elucidate the effect of vacancies. Detailed analyses (X-ray powder and single crystal diffraction, transmission and secondary scanning electron microscopy) of Cr$_{1-x}$ZnSb, $0<x<0.20$, prompts Cr$_{0.86}$ZnSb as the only stable compound, crystallizing with the MnAlGe-type structure. From DFT calculations, an antiferromagnetic spin configuration of Cr local magnetic moments was found to be favorable for both, the perfectly stoichiometric compound CrZnSb, as well as for Cr$_{0.875}$ZnSb. Magnetic order is observed experimentally for Cr$_{0.86}$ZnSb by temperature- and field-dependent magnetization measurements, revealing a magnetic phase transition near 220 K, which is corroborated by zero-field muon spin relaxation studies. Thermoelectric transport properties exhibit distinct maxima in the temperature-dependent Seebeck coefficient and electrical resistivity at around 190 K. Analyzing the measured data on the basis of a triple parabolic band model and DFT simulations, their characteristic features are traced back to a pseudo-gap in the electronic structure arising from a particular vacancy arrangement. These findings offer valuable insights into the role of vacancies in defected materials, contributing to the broader understanding of structural defects and their impact on the electronic structure.