One of the characteristics of transition-metal oxides is a large response
of their physical properties to external fields. The large response occurs
not only for the conjugated variable of the external field (e.g., magnetization
against magnetic field), but also for other properties that might look
unrelated to the external field. For example, some compounds show a drastic
change of electrical resistivity, dielectric constant, and even crystal
structure under magnetic field. These intriguing behaviors arise from the
competition and cooperation between spin, charge, and orbital degrees of
freedom of d electrons in the transition metal. The materials showing this
kind of behaviors are often called “strongly correlated materials”, and
are promising for future "multifunctional" devices.
We are searching for new materials showing a large response of a physical
property (electrical resistivity, dielectric constant, crystal structure,
optical properties, etc.) to an external filed (magnetic field, electric
field, light illumination, etc.) We are also working on the optical investigation
of these materials to clarify the electronic origin of such a large response.