Abstract
We present a new type of colossal magnetoresistance (CMR) arising from an anomalous collapse of the
Mott insulating state via a modest magnetic field in a bilayer ruthenate, Ti-doped Ca3Ru2O7. Such an
insulator-metal transition is accompanied by changes in both lattice and magnetic structures. Our findings
have important implications because a magnetic field usually stabilizes the insulating ground state in a
Mott-Hubbard system, thus calling for a deeper theoretical study to reexamine the magnetic field tuning of
Mott systems with magnetic and electronic instabilities and spin-lattice-charge coupling. This study further
provides a model approach to search for CMR systems other than manganites, such as Mott insulators in
the vicinity of the boundary between competing phases.
