Magnetoelastic coupling in the stretched diamond lattice of TbTaO 4

Abstract

On application of a magnetic field below 2.25 K, the Tb 3+ moments in TbTaO 4 transform from antiferromagnetic to ferromagnetic ordering on a diamond-like lattice. Neutron diffraction data indicate a potential magnetoelastic coupling effect. 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+ (4f 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 λ -shape transitions in d( χT )/d T , d M /d H and specific heat data confirm the previously reported three-dimensional (3D) antiferromagnetic ordering at T N ∼ 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.