1：Experimental Design and Method Selection:

The study used ultrasonication-assisted wet chemical synthesis to synthesize hydroxyapatite (HAp) and cobalt-doped HAp samples. The rationale was to create materials with enhanced properties for biomedical applications, leveraging the flexibility of HAp to incorporate metal ions. Theoretical models included the use of Scherrer formula for crystallite size analysis and standard characterization techniques.

2：Sample Selection and Data Sources:

Samples were synthesized using calcium nitrate tetrahydrate, diammonium hydrogen phosphate, and cobalt(II) nitrate hexahydrate as precursors. Various concentrations of cobalt ions (0.01M, 0.05M, 0.1M) were used to prepare doped samples. Data sources were the synthesized powders characterized through various spectroscopic and magnetic measurements.

3：01M, 05M, 1M) were used to prepare doped samples. Data sources were the synthesized powders characterized through various spectroscopic and magnetic measurements. List of Experimental Equipment and Materials:

3. List of Experimental Equipment and Materials: Equipment included an analytical diffractometer (PANalytical) for XRD, FTIR spectrometer (JASCO FT/IR6300) for infrared spectra, Raman spectrometer with 1064 nm laser excitation, Vibrational Sample Magnetometry (VSM) instrument (Lakeshore VSM 7410) for magnetic measurements, and Ultraviolet Visible spectrophotometer (Jasco 750 series) for optical properties. Materials included calcium nitrate tetrahydrate (Merck), diammonium hydrogen phosphate (Merck), cobalt(II) nitrate hexahydrate (fisher scientific), ammonia solution (Merck), and double distilled water.

4：Experimental Procedures and Operational Workflow:

For HAp synthesis, calcium and phosphate precursors were mixed in a 1:0.6 ratio under stirring and ultrasonication (30% amplitude), with pH maintained at 10 using ammonia. The precipitate was washed, dried at 80°C, and ground. For cobalt-doped HAp, cobalt precursor was added at specified concentrations, following the same procedure. Characterization involved XRD (2θ range 10° to 80°), FTIR (4000-400 cm?1 using KBr pellet), Raman spectroscopy, UV-Vis DRS (200-800 nm), photoluminescence (excitation at 265 nm), and VSM at room temperature with ±2 T field.

5：6 ratio under stirring and ultrasonication (30% amplitude), with pH maintained at 10 using ammonia. The precipitate was washed, dried at 80°C, and ground. For cobalt-doped HAp, cobalt precursor was added at specified concentrations, following the same procedure. Characterization involved XRD (2θ range 10° to 80°), FTIR (4000-400 cm?1 using KBr pellet), Raman spectroscopy, UV-Vis DRS (200-800 nm), photoluminescence (excitation at 265 nm), and VSM at room temperature with ±2 T field. Data Analysis Methods:

5. Data Analysis Methods: Data were analyzed using Scherrer formula for crystallite size from XRD peaks, identification of functional groups from FTIR and Raman spectra, and interpretation of optical and magnetic properties from respective spectra and hysteresis loops.