Enhanced Coercivity Driven by Spin Reorientation in CuCoFe ₂ O ₅ High-Pressure Oxide

We report a comprehensive study of the structural and magnetic properties of CuCoFe 2 O 5, a CaFe 3 O 5 -type mixed-metal oxide obtained at 20 GPa and 1000 °C. Room-temperature single-crystal and powder diffraction measurements confirm the orthorhombic Cmcm framework, with Cu 2+ occupying a distorted CuO 4+2 trigonal prismatic site and Co 2+ /Fe 3+ residing in edge- and corner-sharing octahedral environments. Bond valence and anisotropic displacement analyses reveal pronounced local distortions around Cu 2+, consistent with Jahn–Teller activity. Magnetic measurements indicate two successive transitions: a high-temperature antiferromagnetic order at T N1 = 195 K and a low-temperature spin reorientation at T N2 = 77 K of structural origin, the latter accompanied by a strong bifurcation between field- and zero-field-cooled magnetization curves. Neutron diffraction and DFT+ U calculations demonstrate that the magnetic structure comprises competing Fe–Fe, Fe–Co, and Co–Cu interactions, leading to a canted ferrimagnetic state at low temperature. Moderate magnetic frustration ( f ≈ 3.6) and strong spin–orbit coupling of Co 2+ stabilize large coercivity (∼6.7 T at 2 K). These results highlight the intricate interplay between structural distortions, cation disorder, and competing exchange pathways in determining the complex magnetic ground state of CuCoFe 2 O 5 .