Suppression of antiferromagnetism by pressure in CaCo2 P2

We report magnetization M, heat capacity C, and electrical resistivity ρ for single crystals of the itinerant electron antiferromagnet CaCo2P2 (TN ≈ 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 T1 ≈ 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 γ = 23 mJ/mol·K2, which is large by comparison to closely related 122 analogs and the value predicted by electronic structure calculations. Upon the application of pressure, TN is suppressed toward zero. For P ≥ 0.89 GPa, another phase transition appears at T2 < TN which is also suppressed by P. At Pc ≈ 1.4-1.5 GPa, TN and T2 drop abruptly to zero at a putative quantum phase transition. For P > Pc, a broad shoulder in ρ(T) 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. © 2014 American Physical Society.