Ferromagnetic quantum phase transition in Sr1−xCaxRuO3 thin films

The ferromagnetic quantum phase transition in the perovskite ruthenate Sr1−xCaxRuO3 is studied by lowtemperature magnetization and electrical resistivity measurements on thin films. The films were grown epitaxially on SrTiO3 substrates using metalorganic aerosol deposition and characterized by X-ray diffraction and room temperature scanning tunneling microscopy. High residual resistivity ratios of 29 and 16 for x = 0 and x = 1, respectively, prove the high quality of the investigated samples. We observe a continuous suppression of the ferromagnetic Curie temperature from TC = 160 K at x = 0 towards TC → 0 at xc ≈ 0.8. The analysis of the electrical resistivity between 2 and 10 K reveals T 2 and T 3/2 behavior at x ≤ 0.6 and x ≥ 0.7, respectively. For undoped CaRuO3, the measurement has been extended down to 60 mK, revealing a crossover to T 2 behavior around 2 K, which suggests a Fermi-liquid ground state in this system.