Tunable magnetic orders in CePd$_2$As$_{2-x}$P$_x$

We report the successful synthesis of the polycrystalline compounds CePd$_2$As$_{2-x}$P$_x$ ($0 \leq x \leq 2$) and their physical properties by measuring the transport, magnetic and thermodynamic behaviors as a function of temperature and/or magnetic field. Powder x-ray diffraction (XRD) indicates that CePd$_2$As$_{2-x}$P$_x$ crystallizes in the ThCr$_2$Si$_2$-type tetragonal structure. CePd$_2$As$_2$ exhibits a moderate Sommerfeld coefficient of $γ$ $\approx$ 88 mJ/mol-K$^2$, and undergoes an antiferromagnetic (AFM) transition at the Néel temperature $T_N \approx$ 15 K. Upon substituting As with P, the $T_N$ is nearly unchanged up to $x \simeq 0.6$, while a ferromagnetic (FM) transition develops below $T_N$ for $x \simeq 0.4$. The Curie temperature $T_C$ increases with increasing $x$ and eventually merges with the AFM transition at $x \simeq 0.6$. With further increase of $x$, the system follows typical FM behaviors and its $T_C$ monotonically increases and reaches $T_C \approx 28$ K in CePd$_2$P$_2$. Moreover, a metamagnetic transition is observed in the As-rich samples, but vanishes for $x \geq 0.4$. Such a tunable magnetic ground state may provide an opportunity to explore the possible quantum critical behavior in CePd$_2$As$_{2-x}$P$_x$.