An investigation on structural, optical and magnetic properties of hard-soft SrFe12O19/(CoEu0.02Fe1.98O4)x nanofiber composites.

• Hard-soft SrFe 12 O 19 /(CoEu 0.02 Fe 1.98 O 4) x nanofiber composites were prepared via electrospinning technique. • XRD, SEM and TEM analyses revealed the coexistence of hard and soft phases. • The magnitudes of optical bandgap E g are in the range of 1.56–1.77 eV. • The degree of exchange-coupling between hard and soft phases is well achieved. SrFe 12 O 19 (SFO) nanofibers (NFs), CoEu 0.02 Fe 1.98 O 4 (CEFO) NFs, and hard-soft (H/S) SrFe 12 O 19 (SFO)/(CoEu 0.02 Fe 1.98 O 4) x (CEFO) (x = 1.0, 1.5, 2.0, 2.5) nanofiber composites (NFCs) were produced via electrospinning approach. The X-ray powder diffraction (XRD) patterns for the studied compositions confirmed the coexistence of characteristics peaks of both phases (Sr-M-type hexaferrite and cubic spinel ferrite) without any impurity. The lattice parameters 'a′ and 'c′ for hexagonal SFO and 'a′ for CEFO NFs are fluctuating with increasing the ratio of CEFO NFs. The surface of nanofibers showed fibers having some roughness and bumps. They are consisted of hexagonal particles belong to SFO mixed and fine cubic CEFO NFs. These observations were confirmed by SEM (Scanning electron microscopy) along with EDX (Energy dispersive X-ray) and HR-TEM (High resolution transmission electron microscopy). The fibers showed a non-uniform cross-section with diameter between 33 and 95 nm. Diffuse reflectance spectroscopic (DRS) investigations were performed on SrFe 12 O 19 NFs, on soft CoEu 0.02 Fe 1.98 O 4 NFs, and on H/S (SFO)/(CEFO) (x = 1.0, 1.5, 2.0, 2.5) NFCs. Tauc method provided the estimation of optical bandgap (E g) of each sample. The magnitudes for E g are in the range of 1.56–1.77 eV. The magnetic responses of all samples in external applied magnetic field (M-H) were recorded at ambient temperature (T = 300 K) and low temperature (T = 10 K). Diverse produced nanofiber composites do not display no kinks in the measured M-H curves at both temperatures. Moreover, a single intense peak was clearly observed in the curves of dM/dH vs. H. These results reflected that the degree of exchange-coupling between hard and soft phases is well achieved via the employment of the electrospinning technique. At ambient temperature, it was observed that the magnetization is improving while the coercivity is diminishing with the increase in H/S ratio. On the contrary, at T = 10 K, the rise of CoEu 0.02 Fe 1.98 O 4 content within diverse H/S NFCs provokes a slight decline in magnetization and a great enlargement in coercivity. The plausible reasons for such tendencies were discussed. [ABSTRACT FROM AUTHOR]