Field-induced tricritical behavior in the Néel-type skyrmion host GaV4S8

Abstract

The lacunar spinel compound ${\mathrm{GaV}}_{4}{\mathrm{S}}_{8}$ exhibits a N\'eel-type skyrmion, which holds great promise for future spintronics and ultrahigh-density magnetic memory devices. To gain more insight into the magnetic interactions, the critical behavior of ${\mathrm{GaV}}_{4}{\mathrm{S}}_{8}$ is studied by dc magnetization measurement around the Curie temperature $({T}_{\mathrm{C}})$. A set of reliable critical exponents ($\ensuremath{\beta}=0.220\ifmmode\pm\else\textpm\fi{}0.024$, $\ensuremath{\gamma}=0.909\ifmmode\pm\else\textpm\fi{}0.005$, and $\ensuremath{\delta}=5.161\ifmmode\pm\else\textpm\fi{}0.003$) is obtained by the modified Arrott plot technique, the Kouvel-Fisher method, and critical isothermal analysis. The generated critical exponents fulfill the universality class of tricritical mean-field theory, which suggests a field-induced tricritical phenomenon. Based on the scaling equations, boundaries between the skyrmion and ferromagnetic phases can be distinguished. A tricritical point is revealed at the temperature of ${T}_{\mathrm{Tr}}=12\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ and field of ${H}_{\mathrm{Tr}}=60\phantom{\rule{0.16em}{0ex}}\mathrm{mT}$, which is located at the intersection point among the skyrmion, ferromagnetic, and paramagnetic phases. It is suggested that the origin of the tricritical behavior in ${\mathrm{GaV}}_{4}{\mathrm{S}}_{8}$ is related to the skyrmion state near the magnetic transition temperature ${T}_{\mathrm{C}}$.