Abstract
The ferrimagnetic spinel CoV2 O4 has been a topic of intense recent interest, both as a frustrated
insulator with unquenched orbital degeneracy and as a near-itinerant magnet which can be driven
metallic with moderate applied pressure. Here, we report on our recent neutron diffraction
and inelastic scattering measurements on powders with minimal cation site disorder. Our
main new
result is the identification of a weak ( ∆a ∼ 10−4 ), first order structural phase transition at T
∗ = 90
K, the same temperature where spin canting was seen in recent single crystal measurements. This
transition is characterized by a short-range distortion of oxygen octahedral positions, and
inelastic data further establish a weak ∆ ∼ 1.25meV spin gap at low temperature. Together,
these findings
provide strong support for the local orbital picture and the existence of an orbital glass
state at temperatures below T ∗.
