Synthesis and anisotropic magnetism of single crystalline GdPt2Si2

Single crystals of GdPt${}_2$Si${}_2$ were grown using the Sn flux method, crystallizing in the CaBe${}_2$Ge${}_2$-type tetragonal structure with space group P4/nmm. Electrical resistivity, specific heat, and magnetization data revealed the presence of a double magnetic transition with $T_N\approx 8.4$K and $T_0\approx 6.8$K. Analysis of the specific heat data suggest amplitude-modulated and equal-moment antiferromagnetic orderings, respectively. Field-induced magnetization and magnetic susceptibility data show a metamagnetic transition in the $H\parallel a$ direction at 2 K, as well as the suppression of the magnetic transition located at $T_0$ with increasing external magnetic field. Electron Spin Resonance (ESR) shows the Gd${}^{3+}$ resonance followed by a small second resonance. Peak-to-peak linewidth ($\Delta H_{pp}$) analysis reveals slight broadening at $T\sim 120$ K, indicating an increase in magnetic fluctuations at high temperatures. Ferromagnetic (FM) local polarization at high temperatures is also observed through the $g$-factor analysis, which shows a notable positive shift ($\Delta g$). Our results establish the fundamental physical properties of this material to aid in further understanding of the magnetism in the RPt${}_2$Si${}_2$ series and related non-centrosymmetric systems.