The growth of (010)-oriented CrO2 thin films on Al2O3(0001) substrates lead
s to a higher grain boundary density than the growth of (100)-oriented CrO2
thin films on isostructural TiO2(100) substrates. For both types of films
an intrinsic linear contribution to the high field magnetoresistance (MR) d
ue to spin disorder has been determined at T = 300 K. This contribution doe
s not depend on the crystalline quality of the films and supports the sugge
sted intrinsic double exchange mechanism for CrO2. At low temperature (T =
10 K) intergrain tunneling MR and Lorentz MR appear, which strongly depend
on the crystalline properties of the CrO2 films. (C) 2001 American Institut
e of Physics.