Resistance of a domain wall in La0.7Ca0.3MnO3

Although colossal magnetoresistance (CMR) materials exhibit large changes i n electrical resistance (up to 10(6)%), large magnetic fields (several tesl a) must be applied. To obtain a sizeable low-field effect (< 10(2)% in seve ral millitesla), it is necessary to incorporate structural discontinuities such as grain boundaries, or other types of interfaces. The potential for a pplications, however, remains limited because structural discontinuities in crease electrical resistance by several orders of magnitude and hence creat e noise. Moreover, it has proven to be difficult to fabricate structural di scontinuities reproducibly. We have attempted to investigate discontinuitie s that are purely magnetic via transport measurements through a precisely c ontrolled number of magnetic domain walls of known area in thin film device s of the ferromagnetic CMR perovskite La0.7Ca0.3MnO3. A sharp low-field swi tching seen below similar to 110 K is ascribed to the formation of a precis e number of magnetic domain walls, each with resistance-area product 8 x 10 (-14) Ohm m(2) at 77 K. This is four orders of magnitude larger than expect ed, suggesting that the domain walls contain an additional structure. Our f indings demonstrate that CMR devices are capable of low-noise low-field swi tching, and suggest the possibility of exploiting a hitherto unexpected int rinsic effect reproducibly and therefore commercially. (C) 1999 American In stitute of Physics. [S0021-8979(99)01623-0].