Tricritical wings and modulated magnetic phases in LaCrGe₃ under pressure.

Abstract

Experimental and theoretical investigations on itinerant ferromagnetic systems under pressure have shown that ferromagnetic quantum criticality is avoided either by a change of the transition order, becoming of the first order at a tricritical point, or by the appearance of modulated magnetic phases. In the first case, the application of a magnetic field reveals a wing-structure phase diagram as seen in itinerant ferromagnets such as ZrZn₂ and UGe₂. In the second case, no tricritical wings have been observed so far. Here, we report on the discovery of wing-structure as well as the appearance of modulated magnetic phases in the temperature-pressure-magnetic field phase diagram of LaCrGe₃. Our investigation of LaCrGe₃ reveals a double-wing structure indicating strong similarities with ZrZn₂ and UGe₂. But, unlike these simpler systems, LaCrGe₃ also shows modulated magnetic phases similar to CeRuPO. This finding provides an example of an additional possibility for the phase diagram of metallic quantum ferromagnets.The study of phase transitions in quantum ferromagnets has shown that the approach to a continuous quantum ferromagnetic transition is typically interrupted by either a tricritical point or a new magnetic phase. Here the authors show that LaCrGe₃ exhibits both these features in its phase diagram.