Effect of chemical substitution and pressure on YbRh2Si2

We carried out electrical resistivity experiments on (Yb,La)Rh2Si2 and on Yb(Rh,Ir)2Si2 under pressure and in magnetic fields. YbRh2Si2 exhibits a weak antiferromagnetic transition at atmospheric pressure with a Néel temperature of only $T_N \approx 70$ mK. By applying a small magnetic field TN can be continuously suppressed to $T = 0$ at $B_c = 60$ mT ($B \bot c$) driving the system to a quantum critical point (QCP). On applying external pressure the magnetic phase is stabilized and TN (p) is increasing as usually observed in Yb‐based heavy‐fermion metals. Substituting Yb by La or Rh by Ir allows to create a negative chemical pressure, La (Ir) being smaller than Yb (Rh), and eventually to drive YbRh2Si2 to a pressure controlled QCP. In this paper we compare the effect of external hydrostatic pressure and chemical substitution on the ground‐state properties of YbRh2Si2.