Magnetic field-driven quantum criticality in antiferromagnetic CePtIn4

Abstract

Significance For the past few decades the unsettling thrust to understand the enigmatic physics at the quantum critical point has motivated the condensed-matter research community to explore more about this precarious point of instability. In our attempt to suppress the antiferromagnetic ordering in the compound CePtIn4 by an applied field, we explored a fascinating magnetic phase diagram where the continuous suppression of TN in a second-order mean field-like manner is terminated at a tricritical point which is also a triple point separating antiferromagnetic, paramagnetic, and intermediate metamagnetic sates. Beyond this point, the transition splits into 2 first-order metamagnetic transitions approaching quantum critical end points as T→ 0. Thus, our findings on CePtIn4 evince an extended platform for studying quantum criticality. Physics of the quantum critical point is one of the most perplexing topics in current condensed-matter physics. Its conclusive understanding is forestalled by the scarcity of experimental systems displaying novel aspects of quantum criticality. We present comprehensive experimental evidence of a magnetic field-tuned tricritical point separating paramagnetic, antiferromagnetic, and metamagnetic phases in the compound CePtIn4. Analyzing field variations of its magnetic susceptibility, magnetoresistance, and specific heat at very low temperatures, we trace modifications of the antiferromagnetic structure of the compound. Upon applying a magnetic field of increasing strength, the system undergoes metamagnetic transitions which persist down to the lowest temperature investigated, exhibiting first-order–like boundaries separating magnetic phases. This yields a unique phase diagram where the second-order phase transition line terminates at a tricritical point followed by 2 first-order lines reaching quantum critical end points as T→ 0. Our findings demonstrate that CePtIn4 provides innovative perspective for studies of quantum criticality.