Magnetoelastic coupling in the stretched diamond lattice of TbTaO${}_4$

Abstract

The magnetic structure of diamond-like lattice has been studied extensively in terms of the magnetic frustration. Here we report the distortion of stretched diamond lattice of Tb${}^{3+}$ (4$f^8$) in M-TbTaO${}_4$ on application of a magnetic field. We have investigated the structural and magnetic properties of M phase terbium tantalate M-TbTaO${}_4$ as a function of temperature and magnetic field using magnetometry and powder neutron diffraction. Sharp $\hat{I}»$-shape transitions in $d(\ddot{I}‡T)/dT$, $dM/dH$ and specific heat data confirm the previously reported three-dimensional (3D) antiferromagnetic ordering at $T_N\approx 2.25$ K. On application of a magnetic field the Néel temperature is found to decrease and variable field neutron diffraction experiments below $T_N$ at 1.6 K show an increase in both the bond and angle distortion of the stretched diamond lattice with magnetic field, indicating a potential magneto-elastic coupling effect. By combining our magnetometry, heat capacity and neutron diffraction results we generate a magnetic phase diagram for M-TbTaO${}_4$ as a function of temperature and field.

9 pages main text plus 12 pages supplemental information