Synchrotron X-ray powder diffraction and convergent beam electron diffraction studies on the cubic phase of MgV2O4 spinel

The A V2O4 (A=Mg2+, Zn2+, Cd2+) spinels are three-dimensional spin-1 frustrated systems with orbital degree of freedom, which have been known to possess intriguing orbital states causing releases of spin frustration at low temperatures. We have performed synchrotron X-ray and convergent beam electron diffraction measurements for one of these vanadates, MgV2O4 in order to clarify its crystal structure in the high temperature cubic phase, which is regarded as an important starting point for understanding the details of the low temperature phase. We have successfully observed that the [001] zone axis convergent beam electron diffraction pattern exhibits 4mm symmetry, suggesting the space group of Fd3¯m in the cubic MgV2O4. It has also been demonstrated that the crystal structure of the cubic MgV2O4 contains VO6 octahedra elongated along the threefold rotation axis. Based on our results, we discuss the orbital states of MgV2O4 as well as the other spinel vanadates. - Graphical abstract: Precise geometry of the VO6 octahedra in the cubic phase of MgV2O4 spinel determined with the synchrotron powder XRD data. - Highlights: • We examined the crystal structure of the cubic phase of MgV2O4 spinel. • We prepared the single crystal and powdered sample of MgV2O4 with high quality. • The result of the CBED measurement agrees with the space group of Fd3¯m in the phase. • The cubic phase has VO6 octahedra elongated along the threefold rotation axis