Multiple phase transitions in the vanadium phosphorous oxide*

The vanadium phosphates system (V-P-O) has shown distinct structural stacking and variable valence states of vanadium, providing rich 3d magnetism in this system. V-P-O single crystal was successfully synthesized and characterized by X-Ray diffraction, resistivity, magnetization, heat capacity and neutron scattering measurements. It is a magnetic semiconductor with a band gap of 0.24 eV. Two phase transitions occur at 130 K and 615 K, revealed by transport, susceptibility, and neutron diffraction measurements, suggesting the existence of strongly correlated electrons. In this talk, we will discuss the nature of the phase transitions as well as the light shed by the first principles calculations.