Nanoparticles of LiZnCoFeO (LZC) were prepared by the sol-gel method and dried in a furnace at ∼200 °C. The dried sample was annealed at 500, 600, 700, and 800 °C for 5 h each. Rietveld analysis of X-ray diffraction patterns confirms the cubic Fd3̅m phase formation with lattice parameters ranged from 8.376 up to 8.390 Å and allows the crystallite sizes (d) to be estimated. To enhance microwave (MW) absorption as well as the effectiveness for hyperthermia treatment, nanoparticles are taken in the matrix of multiwalled carbon nanotubes (MWCNTs) and the morphology of the so-prepared samples (LZC@MWCNT) was studied by scanning electron microscopy and transmission electron microscopy analyses. Both static and dynamic magnetic properties were investigated on the samples of LZC nanoparticles and compared to those of the samples of LZC@MWCNT. The samples annealed at 500, 600, and 800 °C are excellent candidates in cancer treatment as ac magnetic heating analysis shows that the hyperthermia temperature (42 °C) was successfully achieved for an applied ac magnetic field of 420 Oe and 300 kHz frequency. MW absorption study also reveals that the samples of LZC@MWCNT could be used as a potential MW absorbing material for which a maximum reflection loss (R) of ∼-21 dB was achieved at a frequency of 15.27 GHz for only 1 mm layer thickness.

Two spices trivalent transition metal ions, nonmagnetic Al 3+ , Bi 3+ and magnetic Cr 3+ , Mn 3+ substituted barium hexaferrite powders are synthesised via dynamic hydrothermal method then calcinated at different temperatures. Powder XRD patterns analysis and Rietveld refinement indicate magnetoplumbite-type crystalline phase. The crystallite size calculated using Scherer's formula varies from 153 to 248 nm as it is affected by the ionic radius of trivalent metal ions and calcination temperatures. The morphological features show agglomerations of spherical-shaped particles with an average size of 400 ± 50 nm for BaBiFe 11 O 19 and hexagonal-shaped particles 1-2µm for the other substitutions. Magnetic studies show a ferromagnetic behaviour for all samples. The nonmagnetic Al 3+ , Bi 3+ substituted materials have lower saturation magnetization Ms and remanence Mr than the magnetic substitutions Cr 3+ , Mn 3+. These results reveal that Ms and Mr are related to the magnetic moment of each metallic ion and its distribution in the lattice. For magnetic substitution, Ms of manganese substitution (61.10 emu/g) is found higher than that of chromium (60.33 emu/g) since Mn 3+ has a magnetic moment of 5µ B greater than Cr 3+ with 3µ B. Coercivity Hc and maximum energy product (BH) max determined from M-H loops exhibit an increasing trend with calcination temperature as they are related to the crystallite size. Hc and (BH) max of BaMnFe 11 O 19 are found maximum 0.426 T and 7.47 kJ.m-3 , respectively.