Thermodynamic Properties, Mössbauer Study, and First-Principles Calculations of TlFe(MoO4)2

We report the results of magnetization and specific heat measurements, a 57Fe Mossbauer study of hyperfine interactions and density functional theory calculations in TlFe(MoO4)2 demonstrating two magnetic phase transitions at TN2 = 5.7 K and TN1 = 6.2 K. In the asymptotical critical region TN2 ≤ T ≤ TN1, the temperature dependence of the average hyperfine magnetic field ⟨Bhf(T)⟩ at the 57Fe nuclei is well-described by the power law ⟨Bhf(T)⟩ ∝ tβ with the static critical exponent β ≈ 0.37 inherent for a three-dimensional magnet. In this range, the Mossbauer spectra are described in terms of collinear spin-density-wave with the inclusion of high-order harmonics. The spectra of the low-temperature phase, below TN2, are well-fitted by a single six-line Zeeman pattern reflecting the equivalence of magnetic sites occupied by Fe3+ ions in an antiferromagnetic structure. The first-principles calculations allowed estimation of the strength of main exchange interactions.