Critical scaling analysis of the itinerant ferromagnet Sr1-x Cax RuO3

The critical behavior of Sr1-xCaxRuO3 was investigated by a scaling analysis based on the Arrott-Noakes equation of state. The critical exponents β, γ, and δ of the magnetic critical behavior were extracted for samples with 0 ≤x≤0.6. The ferromagnetic system exhibits a smooth suppression of the Curie temperature TC to zero at a critical concentration xc ≈ 0.7. The ordered magnetic moment decreases simultaneously as expected for itinerant ferromagnets, however, does not vanish completely at xc, indicating small magnetic clusters or inhomogeneities. For x = 0, mean-field like exponents are observed. With increasing x, the critical exponents β, γ, and δ vary nearly linearly from β ≈ 0.5, γ ≈ 1, and δ ≈ 3 for x = 0 to β ≈ 1, γ ≈ 0.9, and δ ≈ 1.6 for x ≈ 0.6. The Widom scaling relation is always met for x≤0.6. Despite the systematic evolution of the critical exponents as a function of x, the exponents cannot be described by any of the universality classes known for classical standard models. The particular trend of the effective critical exponents may be possibly explained by a strong-disorder line of fixed points; the vicinity to xc suggests that this behavior is caused by the vicinity to a quantum phase transition.