Development of the critical exponent at the antiferromagnetic phase transition of YbRh2Si2 under chemical pressure

Abstract

AbstractWe present specific‐heat measurements in the vicinity of the antiferromagnetic phase transition on single crystals of the alloy Yb(Rh1−xCox)2Si2 for x ≤ 0.38. This study was motivated by the violation of critical universality in the undoped YbRh2Si2 [Krellner et al., Phys. Rev. Lett. 102, 196402, 2009] where we have found a large critical exponent α = 0.38. For Co‐doped samples we observe a drastic change of the critical fluctuations resulting in a negative α, explainable within the universality classes of phase transitions. The development of α under chemical pressure gives strong indication that the violation of critical universality in YbRh2Si2 is due to the nearby quantum critical point.