Field-induced tricritical behavior in the Néel-type skyrmion host GaV 4 S 8

The lacunar spinel compound ${\\mathrm{GaV}}_{4}{\\mathrm{S}}_{8}$ exhibits a N\\\u0027eel-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 ${T}_{\\mathrm{C}}$.