Spin Reorientation in Antiferromagnetic Layered FePt5P

FePt5P, a substitutional variant of the anti-CeCoIn5 structure type in the space group P4/mmm, was synthesized by a high-temperature solid-state method and structurally characterized by X-ray diffraction. FePt5P contains layers of FePt12 clusters formed by magnetically active Fe and heavy Pt with strong spin-orbit coupling (SOC); the layers are separated by P atoms. The various Fe-Pt distances in FePt12 clusters generate complex magnetic orders in FePt5P. According to temperature-dependent magnetic and specific heat measurements, FePt5P shows a stripe-type antiferromagnetic order at TN ≈ 90 K, which is also confirmed by resistivity measurements. Moreover, a spin reorientation occurs at ∼74 and ∼68 K in and out of the ab plane based on the specific heat measurements. The temperature-dependent neutron powder diffraction patterns demonstrate the antiferromagnetic order in FePt5P, and the spins orientate up to 58.4° with respect to the c axis at 10 K. First-principles calculations of FePt5P show the band splitting at the Fermi level by strong SOC and the s-d hybridization between P and Fe/Pt electrons enhances the structural stability and affects the magnetic ordering.