Doping-induced quantum crossover in Er2Ti2−xSnxO7

We present the results of the investigation of magnetic properties of the Er2Ti2−xSnxO7 series. For small doping values, the ordering temperature decreases linearly with x, while the moment configuration remains the same as in the x=0 parent compound. Around x=1.7 doping level, we observe a change in the behavior, where the ordering temperature starts to increase and new magnetic Bragg peaks appear. For the first time, we present evidence of a long-range order (LRO) in Er2Sn2O7 (x=2.0) below TN=130 mK. It is revealed that the moment configuration corresponds to a Palmer-Chalker type with a value of the magnetic moment significantly renormalized compared to x=0. We discuss our results in the framework of a possible quantum phase transition occurring close to x=1.7.