Magnetic and Fermi Surface Properties of EuSnP with the First-Order Antiferromagnetic Transition and SrSnP with a Nearly Cylindrical Fermi Surface

Experiments were carried out for an antiferromagnet EuSnP and a non-4 f reference compound SrSnP with the tetragonal structure. We found metamagnetic transitions in the antiferromagnetic state for both H ∥ [001] and [110] in EuSnP, suggesting a noncollinear configuration of magnetic moments. The magnetic phase boundary near a Néel temperature T_N = 20.3 K is vertical in the H vs T phase diagram, which is characteristic in the first-order antiferromagnetic transition at T_N. The present antiferromagnetic state is stable against pressure P, revealing the high Néel temperature of T_N = 140 K at P = 13.5 GPa. A nearly cylindrical electron Fermi surface in SrSnP is also characteristic, which is observed by the de Haas–van Alphen effect in a wide angle range from [001] (θ = 0°) to θ = 81°, close to [110] and [100]. The Yamaji effect is observed at θ₁ = 30°, θ₂ = 54°, and θ₃ = 66°.