Effect of off-stoichiometry on structural, transport, and magnetic properties of altermagnetic CrSb

Abstract

We investigate the effects of Cr off-stoichiometry on the structural, magnetic, thermodynamic, and electrical transport properties of the antiferromagnetic compound CrSb. Single-phase hexagonal NiAs-type structure is stabilized only in the Cr-rich regime, where excess Cr atoms preferentially occupy the interstitial trigonal bipyramidal 2?d sites, as confirmed from the x-ray diffraction study. Synchrotron-based x-ray absorption fine-structure measurements reveal a progressive increase in local structural disorder with increasing Cr concentration, particularly within the Cr sublattice. Magnetization measurements show a pronounced low-temperature upturn in susceptibility and nonlinear field-dependent behavior, which can be consistently described by the formation of short-range magnetic clusters associated with interstitial Cr moments embedded in the antiferromagnetic CrSb matrix. Specific-heat measurements indicate a finite electronic density of states at the Fermi level with a nonmonotonic evolution of the Sommerfeld coefficient with Cr content, reflecting the interplay between electronic delocalization and disorder-induced localization. Electrical transport measurements confirm metallic conduction across all compositions and reveal the emergence of an antiferromagnetic gap at low temperatures with increasing Cr concentration. These results demonstrate a strong coupling between off-stoichiometry, local structural disorder, magnetic correlations, and charge transport in Cr sub(1+x)?Sb and establish controlled Cr occupancy as an effective route for tuning magnetic interactions and electronic responses relevant to altermagnetic systems.