Recently discovered magnetoelectricity in the rare-earth aluminum borates RAl${}_3$(BO${}_3$)${}_4$ has attracted attention due to the large values of magnetoinduced electric polarization. We have observed for the first time the magnetoelectric polarization in TbAl${}_3$(BO${}_3$)${}_4$ exhibiting anomalous temperature dependence: an electric polarization induced by in-plane magnetic field ($P\left|\right|a,H\perp c$ axis) which is small at low temperatures ($4\mathrm{K}$), remarkably increases by almost an order of magnitude at high temperatures ($150–300\mathrm{K}$). The observed nonmonotonic temperature behavior of the field-induced polarization, including a change of sign at $\sim 65–70\mathrm{K}$, is attributed to the competition of the ground and excited crystal-field states of Tb${}^{3+}$ ions. Quantum theory analysis, involving the combination of analytical and numerical methods, has enabled us to quantitatively describe the observed magnetic and magnetoelectric properties of TbAl${}_3$(BO${}_3$)${}_4$.

• Received 13 September 2013
• Revised 3 January 2014

DOI:https://doi.org/10.1103/PhysRevB.89.014418