Susceptibility, high-field magnetization and ESR studies in a spin-5/2 triangular-lattice antiferromagnet Ba3MnSb2O9

The polycrystalline Ba3MnSb2O9 system as a spin-5/2 quasi-two dimensional triangular-lattice antiferromagnet (TLAF), is investigated by means of magnetic susceptibility, specific heat, high field magnetization and electron spin resonance (ESR) measurements. The ac susceptibility and specific heat studies reveal that it undergoes an AFM transition at TN=10.2 K rather than the spin-glass one. High-field magnetization at 4.2 K exhibits a weak 1/3 magnetization step near ~16.5 T indicative of the field-induced quantum phase transition behavior. The analysis of temperature dependence of ESR spectra suggests that the short-range antiferromagnetic (AFM) correlation appear at temperatures well above TN. Further high-field ESR measurement up to 25 T at 4.2 K shows a broad resonance line, and the obtained g value is 2.094±0.012. Combined with the magnetic susceptibility and specific heat, the magnetic state below TN is explained by an AFM long rang order or a well developed AFM short range order with small anisotropy.