Structure of Multiferroic RAl3(BO3)4 and RFe3(BO3)4 in the Region of High Electric Polarization

The multiferroic system RAl$_{\mathrm{3}}$(BO$_{\mathrm{3}})_{\mathrm{4}}$ is known to exhibit a strong coupling of magnetic field to the electrical polarization at low temperature (below \textasciitilde 100 K). A giant magnetoelectric effect was found in this$_{\mathrm{\thinspace }}$system. Recent work by us (PRB B \textbf{92} 104108) reveals evidence for changes in the local structure at low temperature. In this work we explore the structural changes using single crystal diffraction and other structural probes. Comparisons between the Fe and Al based systems will be made. This work is supported by DOE Grant DE-FG02-07ER46402.