Coupling between Orbital and Spin Degrees of Freedom in Jahn-Teller Ions for Co 1 − x Fe x V 2 O 4

It is found that a small distortion caused by magnetostriction and a structural phase transition caused by Jahn-Teller distortion are continuously connected in Co_{1-x}Fe_{x}V_{2}O_{4} under variation of x. Spin-orbit coupling in Jahn-Teller-active Fe^{2+} ions gives rise to this novel correlation between spins, orbitals, and the lattice distortion in this series of compounds.