Stoner–Wohlfarth rotation or domain wall motion mechanism in W-type magnetic hexaferrite nanoparticles

Highly magnetized SrCo2−xMnxFe16O27 (x=0–0.5) W-type ferrite was synthesized by a chemical co-precipitation method followed by a hot press technique. The role of substitution of Mn captions on the thermal, structural and magnetic properties of nanoparticles was characterized by TGA/DTA, X-ray diffraction (XRD), Fourier transformed infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), electron diffraction pattern and vibrating sample magnetometer (VSM). Single phase of W-type ferrite was formed based on the XRD accuracy. According to the TEM micrograph evaluation, it was found that the particle size was in the range of 15–25 nm, with an irregular configuration. In-plane and out-of-plane magnetic hysteresis loops for bulk ferrite were measured at a room temperature up to a maximum applied field of 24 kOe. It was found that the samples with composition of x=0–0.3 have perpendicular anisotropy, while the rest of samples have in-plane anisotropy. Angular dependence of coercivity and initial magnetization curves proved that the highly magnetized bulked ferrite with x=0 to 0.3 obey the Stoner–Wohlfarth mechanism, while x=0.4 and 0.5 follow the domain wall motion rule.