We report magnetization $M$, heat capacity $C$, and electrical resistivity $\rho$ for single crystals of the itinerant electron antiferromagnet ${\text{CaCo}}_2$${\text{P}}_2$ ($T_{\mathrm{N}}$ $\approx$ 110 K). Measurements at ambient pressure reveal rich magnetic behavior, where ferromagnetic correlations are present in the paramagnetic state and a subsequent feature is seen at $T_1$ $\approx$ 22 K within the ordered state. Heat-capacity measurements additionally reveal moderately enhanced electronic correlations, as evidenced by the electronic coefficient of the specific heat $\gamma$ $=$ 23 mJ$/$mol$·$K${}^2$, which is large by comparison to closely related 122 analogs and the value predicted by electronic structure calculations. Upon the application of pressure, $T_{\mathrm{N}}$ is suppressed toward zero. For $P$ $\ge$ 0.89 GPa, another phase transition appears at $T_2$ $<$ $T_{\mathrm{N}}$ which is also suppressed by $P$. At $P_{\mathrm{c}}$ $\approx$ 1.4–1.5 GPa, $T_{\mathrm{N}}$ and $T_2$ drop abruptly to zero at a putative quantum phase transition. For $P$ $>$ $P_{\mathrm{c}}$, a broad shoulder in $\rho \left(T\right)$ appears at $T^{*}$, which moves to higher $T$ and broadens with increasing $P$. We discuss possible scenarios to understand the phase diagram and compare to other compounds which show similar $P$-driven behavior.

• Received 4 December 2013
• Revised 17 February 2014

DOI:https://doi.org/10.1103/PhysRevB.89.094408