Anisotropy of electrical and magnetic transport properties of epitaxial SrRuO₃ thin films

SrRuO₃ (SRO) thin films with different thickness (2–70 nm) have been grown on (001), (110), and (111) SrTiO₃ substrates. The (001)-SRO films (2–8 nm) exhibited smooth flat surfaces whereas the (110)- and (111)-SRO films featured a faceted island structure. Room temperature resistivity and residual resistivity are the lowest for the (111)-SRO films (30–70 nm). Over all thicknesses, we observed enhanced magnetization in the (111)-SRO films (∼4 μ_B/Ru) compared with that for the (001)- and (110)-SRO films (∼2 μ_B/Ru and ∼3 μ_B/Ru, respectively), suggesting a low-spin state t_2g(3↑,1↓), high-spin state t_2g(3↑)e_g(1↑), and mixed low- and high-spin states for the (001)-, (111)-, and (110)-SRO films, respectively. The dependence of resistivity on temperatures near T_C follows a power law with exponent β = 0.312 and β = 0.363 for the (110)- and (111)-SRO films, respectively. These critical exponents are consistent with magnetic data with scaling law M = C (T_C − T)^β. At low temperatures, dM/dT and dρ/dT show a linear relationship in the temperature range for the Fermi liquid. These results suggest that the intrinsic electrical and magnetic transport properties are coupled