Magnetic ground state of PbVO$_{3}$ and origin of the large tetragonal distortion

Magnetic property of PbTiO$_{3}$-type perovskite PbVO$_{3}$ with a large tetragonal distortion ($c/a$ = 1.23)$^{1}$ was investigated. Long-range antiferromagnetic ordering with $T_{N}$ = 45 K was found by a $\mu $SR measurement. Magnetic susceptibility of multi domain crystal showed a broad maximum centered at 180 K indicated the 2-dimensional nature in magnetism. This is consistent with the $d_{xy}$ orbital ordering predicted by the band calculation.$^{2}$ We propose a mechanism that the pyramidal coordination with a short vanadium-apical oxygen bond is stabilized to lift the orbital degeneracy in this $d^{1}$ system. Accordingly, PbMnO$_{3}$ (Mn$^{4+}$, $d^{3})$ newly stabilized at 15 GPa has a pseudo cubic structure like PbCrO$_{3}$. This scenario explains the pressure induced tetragonal to cubic, insulator to metal transition$^{1}$ of PbVO$_{3}$ and similar large tetragonal distortion of BiCoO$_{3}$. [1]A. A. Belik, \textit{et al., Chem. Mater.}, \textbf{18} (2006) 798. [2]Y. Uratani, \textit{et al.}, \textit{Jpn. J. Appl. Phys.}, \textbf{44} (2005) 7130.