Magnetic study of M-type Ru–Ti doped strontium hexaferrite nanocrystalline particles

• A systematic study was done on the effect of the substitution of Ti2+ and Ru4+ for Fe3+ in SrM.
• Full structural refinement was carried out.
• The magnetic properties were studied in a wide range of temp. and magnetic fields.
• The saturation magnetization and the coercivity strongly depend on Ru–Ti substitution.
• A clear understanding on the cationic distributions and magnetic behavior was obtained.

We carried out a systematic study on the effect of the substitution of Ti2+ and Ru4+ ions for Fe3+ ions on the structural and magnetic properties of the strontium ferrite SrFe12−2xRuxTixO19 nanoparticles with (0≤x≤0.30≤x≤0.3), using x-ray diffraction, Quantum Design PPMS-9 magnetometry, and electrical resistivity. A clear irreversibility between the zero-field-cooled and field-cooled curves was observed below room temperature and the zero-field-cooled magnetization curves displayed a broad peak at a temperature TM. These results were discussed within the framework of random particle assembly model and associated with the magnetic domain wall motion. The resistivity data showed some kind of a transition from insulator to perfect insulator around TMTM. The high-temperature magnetization measurements exhibited sharp peaks just below Tc indicating a superparamagnetic behavior. With Ru–Ti substitution, the saturation magnetization at 5 K showed small variations were it slightly increased with increasing x up to 0.2, and then decrease for x = 0.3, while the coercivity decreased monotonically, recording a reduction of about 78% at x = 0.3. These results were discussed in light of the cationic distributions based on the results of the structural refinements.

(a) Zero-field-cooled and field-cooled magnetizations of SrFe12−2xRuxTixO19 as a function of temperature measured at 100 Oe for x = 0.3. (b) Thermomagnetic magnetizations measurements of SrFe12−2xRuxTixO19 with different concentrations. (c) Saturation magnetization and coercivity of SrFe12−2xRuxTixO19 as a function of Ru–Ti concentration (x). (d) Anisotropy field and the first anisotropy constant of SrFe12−2xRuxTixO19 as a function of Ru–Ti concentration (x).Figure optionsDownload as PowerPoint slide