Triangular Magnet Emergent from Noncentrosymmetric Sr 0.94 Mn 0.86 Te 1.14 O 6 Single Crystals.

We report the successful growth of high-quality single crystals of Sr 0.94 Mn 0.86 Te 1.14 O 6 (SMTO) using a self-flux method. The structural, electronic, and magnetic properties of SMTO are investigated by neutron powder diffraction (NPD), single-crystal X-ray diffraction (SCXRD), thermodynamic, and nuclear magnetic resonance techniques in conjunction with density functional theory calculations. NPD unambiguously determined octahedral (trigonal antiprismatic) coordination for all cations with the chiral space group P 312 (no. 149), which is further confirmed by SCXRD data. The Mn and Te elements occupy distinct Wyckoff sites, and minor anti-site defects were observed in both sites. X-ray photoelectron spectroscopy reveals the existence of mixed valence states of Mn in SMTO. The magnetic susceptibility and specific heat data evidence a weak antiferromagnetic order at T N = 6.6 K. The estimated Curie-Weiss temperature θ CW = -21 K indicates antiferromagnetic interaction between Mn ions. Furthermore, both the magnetic entropy and the 125 Te nuclear spin-lattice relaxation rate showcase that short-range spin correlations persist well above the Néel temperature. Our work demonstrates that Sr 0.94(2) Mn 0.86(3) Te 1.14(3) O 6 single crystals realize a noncentrosymmetric triangular antiferromagnet.