Avoided ferromagnetic quantum critical point in pressurized La5Co2Ge3

Abstract

We present the pressure-temperature phase diagram ${\mathrm{La}}_{5}{\mathrm{Co}}_{2}{\mathrm{Ge}}_{3}$ up to $\ensuremath{\sim}5$ GPa, which was constructed from magnetization, resistivity, and specific heat measurements. At ambient pressure, ${\mathrm{La}}_{5}{\mathrm{Co}}_{2}{\mathrm{Ge}}_{3}$ is an itinerant ferromagnet with a Curie temperature ${T}_{\text{C}}\ensuremath{\sim}$ 4 K. Upon increasing pressure up to $\ensuremath{\sim}1.7$ GPa, ${T}_{\text{C}}$ is suppressed down to $\ensuremath{\sim}3$ K. Upon further increasing pressure, our results suggest that ${\mathrm{La}}_{5}{\mathrm{Co}}_{2}{\mathrm{Ge}}_{3}$ enters a different low-temperature ground state. The corresponding transition temperature ${T}^{*}$ has a nonmonotonic pressure dependence up to $\ensuremath{\sim}5$ GPa. Our results demonstrate that the ferromagnetic quantum critical point in ${\mathrm{La}}_{5}{\mathrm{Co}}_{2}{\mathrm{Ge}}_{3}$ is avoided by the appearance of a different, likely magnetically ordered, state that has an antiferromagnetic component.