Magnetic-field- and temperature-dependent Raman scattering studies of ${\mathrm{C}\mathrm{a}}_3{\mathrm{R}\mathrm{u}}_2{\mathrm{O}}_7$ 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 ($H_o\Vert \mathrm{\text{hard axis}}$), and a reentrant orbital-ordered to orbital-disordered to orbital-ordered transition ($H_o\Vert \mathrm{\text{easy axis}}$). 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.

• Received 7 June 2004

DOI:https://doi.org/10.1103/PhysRevLett.93.167205