Coupling between Orbital and Spin Degrees of Freedom in Jahn-Teller Ions for <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>Co</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>1</mml:mn> <mm

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.