  Recently, electrically conducting heterointerfaces between dissimilar
band-insulators (such as lanthanum aluminate and strontium titanate) have
attracted considerable research interest. Charge transport has been thoroughly
explored and fundamental aspects of conduction firmly established. Perhaps
surprisingly, similar insights into conceptually much simpler conducting
homointerfaces, such as the domain walls that separate regions of different
orientations of electrical polarisation within the same ferroelectric
band-insulator, are not nearly so well-developed. Addressing this disparity, we
herein report magnetoresistance in approximately conical 180o charged domain
walls, which occur in partially switched ferroelectric thin film single crystal
lithium niobate. This system is ideal for such measurements: firstly, the
conductivity difference between domains and domain walls is extremely and
unusually large (a factor of at least 1013) and hence currents driven through
the thin film, between planar top and bottom electrodes, are overwhelmingly
channelled along the walls; secondly, when electrical contact is made to the
top and bottom of the domain walls and a magnetic field is applied along their
cone axes (perpendicular to the thin film surface), then the test geometry
mirrors that of a Corbino disc, which is a textbook arrangement for geometric
magnetoresistance measurement. Our data imply carriers at the domain walls with
extremely high room temperature Hall mobilities of up to ~ 3,700cm2V-1s-1. This
is an unparalleled value for oxide interfaces (and for bulk oxides too) and is
most comparable to mobilities in other systems typically seen at cryogenic,
rather than at room, temperature.
