Abstract
VOCl develops magnetic order below . Employing single-crystal x-ray diffraction and powder neutron diffraction it is shown that the magnetic phase transition is accompanied by a small, temperature-dependent monoclinic lattice distortion with at . The phase transition presumably is of second order with a critical exponent . The monoclinic distortion lifts the frustration of interchain interactions along of the orthorhombic room-temperature structure with the result that chains of antiferromagnetic order exist along while ferromagnetic chains exist along . Both antiferromagnetic interchain coupling (if stronger along than along ) and ferromagnetic interchain coupling (if stronger along than along ) can explain the observed magnetic superstructure with magnetic space group on the supercell (standard setting ) and with magnetic moments parallel to . Remarkably, the lattice distortion is not accompanied by a structural distortion so that the driving force for the lattice distortion is completely governed by the magnetic interactions.
- Received 3 April 2009
DOI:https://doi.org/10.1103/PhysRevB.80.064426
©2009 American Physical Society