Te125Mössbauer Effect in Paramagnetic and Antiferromagnetic MnTe2

Abstract

The Mössbauer effect associated with the 35.6-keV ($\frac{3}{2}\to \frac{1}{2}$) transition in ${\mathrm{Te}}^{125}$ is applied to extract the electronic structure and the induced magnetic features of the ditelluride ligand in antiferromagnetic Mn${\mathrm{Te}}_2$ ($T_N=83.8\mathrm{}°$K). Measurements above $T_N$ at 90.1°K, reveal a quadrupole split spectrum with $\left|e^{2}qQ\right|=15.5\mathrm{}$ mm/sec. Absorption spectra obtained below $T_N$ result from a combination of a magnetic dipole interaction and a predominant electric quadrupole interaction with negative $e^2\mathrm{qQ}$. At 4.2°K ($\frac{T}{T_N}=0.05\mathrm{}$) and 20.3°K ($\frac{T}{T_N}=0.24\mathrm{}$) the internal magnetic field $H=114\mathrm{}\pm 7$ kOe and the angle $\theta$ formed with $q_{\mathrm{zz}}$ is ${30\mathrm{°}}_{-5\mathrm{}}^{+3\mathrm{}}$. At 77.3°K ($\frac{T}{T_N}=0.925\mathrm{}$), $H=55\mathrm{}\pm 3$ kOe, and $0°\le \theta <10\mathrm{}°$. The sign and magnitude of the quadrupole coupling constant as well as the observed anisotropy in the recoilless fraction are consistent with the "molecular" conception of the ${\mathrm{Te}}^{1-}$-${\mathrm{Te}}^{1-}$ anion. Comparison of $H$ in ${\left({\mathrm{Te}}^{125}\right)}^{1-}$ and $H$ in substituted ${\left({\mathrm{I}}^{129}\right)}^{1-}$ (obtained from a separate experiment) suggests a transferred hyperfine interaction mechanism involving the unpairing of the ligand $5s$ orbitals. The resulting angle $\theta$ was found to be inconsistent with the suggested model of the spin arrangement as deduced from a neutron-diffraction pattern in powder samples by other authors.