We present results of temperature and magnetic held dependent resistiv
ity rho(H,T) and bulk magnetization M(H,T) measurements on post-anneal
ed La0.7Ca0.3MnO3 thin films that were grown via pulsed-laser depositi
on. Both the resistivity and the anomalously large negative magnetores
istance peak near the ferromagnetic ordering temperature (T-c=250 K),
with Delta rho/rho(0)=-85% at 50 kOe. A clear correlation is found bet
ween rho and M that is described by the phenomenological expression rh
o(H,T)(proportional to)exp[-M(H,T)/M(0)]. This correlation reflects th
e important interplay between transport and magnetism in this system,
and suggests that the transport below T-c involves polaron hopping. (C
) 1995 American Institute of Physics.