Grain-Boundary Magnetoresistance of CrO₂ Films Grown on TiO ₂-Buffered LaAlO₃ Substrates

The magnetic and magnetotransport properties of predominantly (110)-oriented CrO₂ films grown on TiO₂-buffered LaAlO₃ substrates were investigated. The atomic force microscopic images revealed that the as-grown CrO₂ films are granular. The magnetic measurements indicated that in-plane coercive fields are about 60 Oe and 100 Oe at 300 K and 7 K, respectively. The as-grown films are semiconductive below 75 K; a magnetoresistance with a ΔR/R₀ ratio of -13 % in a magnetic field of 5 T was observed at 5 K, which is absent in high-quality epitaxial films. The coincidence between the coercive field and the peaks of the magnetoresistive loop measured at low temperatures indicates that spin-dependent scattering plays a crucial role in the transport properties.