Interplay of Structural and Magnetic Contributions of Second Harmonic Generation in Noncentrosymmetric BaMnSb

BaMnSb₂ is a magnetic topological semimetal with noncentrosymmetric symmetry. It exhibits canted antiferromagnetic (AFM) ordering, with a Néel temperature (T_N) of 295 K. The spin alignment is characterized by an AFM projection perpendicular to the ac plane, while the in-plane projection is ferromagnetic. We conducted second harmonic generation (SHG) polarimetry on BaMnSb₂ single crystals. Due to the combined effects of broken inversion and time-reversal symmetries, both structural and magnetic contributions were observed in the SHG signal. In addition to the anticipated increase in the magnetic contribution below T_N, we also detected a distinctive drop in the SHG signal around T_N, likely the result of the destructive interference between the two contributions.