Co‐Doped (Na ⁺ , Mg ²⁺ , Zn ²⁺ , Fe ³⁺ )‐Carbonated Hydroxyapatites and Composites with M ^II Fe ₂ O ₄ : Synthesis, Mechanic, Magnetic, and Antibacterial Properties for Medical Application

Co‐doped (Na + , Mg 2+ , Zn 2+ , Fe 3+ , CO 3 2‐ )‐calcium phosphates and their composites with 10 or 25 wt% of (Mg/Zn)Fe 2 O 4 were synthesized via a one‐step method from aqueous solutions and heated to 600°C. X‐ray powder diffraction (XRD) analysis confirmed the formation of single‐phase modified hydroxyapatites and biphasic calcium phosphate composites with a ferrite phase. The composite based on modified biphasic calcium phosphate with 10 wt% of ZnFe 2 O 4 exhibited a higher hardness (HV = 3.28 GPa) than the corresponding co‐doped (Na + , Mg 2+ , Zn 2+ , Fe 3+ )‐hydroxyapatite (HV = 2.49 GPa) and a composite of modified biphasic calcium phosphate with 25 wt% ZnFe 2 O 4 (HV = 2.91 GPa). The magnetic properties, studied by the Faraday method, showed that the composite with 25 wt% MgFe 2 O 4 possessed a significantly higher magnetic susceptibility (345.9) than its ZnFe 2 O 4 counterpart (77.8). Furthermore, an increase in the β ‐Ca 3 (PO 4 ) 2 ‐based phase in the 25 wt% M II Fe 2 O 4 composites was found to enhance the material's activity toward partial dissolution, a key factor in bone engineering. The antibacterial evaluation against Staphylococcus aureus and Pseudomonas aeruginosa demonstrated the functional potential of co‐doped (Na + , Mg 2+ , Zn 2+ , Fe 3+ , CO 3 2‐ )‐hydroxyapatites and composites based on modified biphasic calcium phosphates with 25 wt% M II Fe 2 O 4 . These results contribute to the development of safe materials with tailored magnetic, mechanical, and biomedical properties.