Field-Induced Orbital and Magnetic Phases in Ca₃Ru₂O₇

Magnetic-field- and temperature-dependent Raman scattering studies of Ca₃Ru₂O₇ reveal dramatic field-dependent properties arising from transitions between various complex orbital and magnetic phases, including a field-induced orbital-ordered to orbital-disordered transition (H_o‖  hard axis), and a reentrant orbital-ordered to orbital-disordered to orbital-ordered transition (H_o‖  easy axis). We find that the dramatic magnetic-field properties are most prevalent in a “mixed”-magnetic and -orbital phase regime, providing evidence for a strong connection between orbital phase inhomogeneity and “colossal” field effects in the ruthenates.