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In this work, M-type hexagonal ferrite nanoparticles having the composition ${\mathrm{\text{Ca}}}_{0.25}{\mathrm{\text{Ba}}}_{0.75}{\mathrm{\text{Cr}}}_x{\mathrm{\text{Fe}}}_{12-2x}{\mathrm{\text{O}}}_{19}$, where $x=(0.0,0.05,0.10,0.15,0.20)$ were fabricated by the sol–gel auto-combustion technique. The influence of chromium doping on structural, dielectric and magnetic characteristics was examined. XRD powder analysis revealed the geometry of single-phase hexaferrite with P63/mmc space group. The magnetoplumbite hexagonal structure was revealed by the X-ray diffraction analysis. Crystallite size, $a$ & $c$ lattice parameters, bulk density, X-ray density, cell volume and porosity were assessed. Crystallite size ranged from 39.54nm to 42.91nm. The X-ray density and bulk density were enhanced while porosity was decreased with the substitution of ${\mathrm{\text{Cr}}}^{3+}$cation. The morphology of the fabricated materials was inspected by the SEM analysis, which displays uniformly scattered particles with hexagonal platelet shape. The value of the dielectric constant is high in the low-frequency regime, and it decreases with increasing frequency. The dielectric constant decreased appreciably with the increase of ${\mathrm{\text{Cr}}}^{3+}$. Such observed dielectric and magnetic features are useful for different technological applications like microwave absorbers, voltage-controlled, dielectric resonators and recording media.

EPR and magnetic susceptibility measurements on xMnO·(100-x)[70TeO₂·25B₂O₃·5SrF₂] glasses, within 0.1 ≤ x ≤ 50 mol% were performed. The number of isolated Mn²⁺ ions, participating at the g ≈ 4.3 resonance increases up to 1 mol% MnO and after that decreases to nil for 10 mol% MnO. The number of Mn²⁺ ions participating at the g ≈ 2.0 resonance increases when the MnO content rises. From line-width composition dependence of these glasses, for x > 3 mol%, the manganese ions participate in the superexchange magnetic interaction. Magnetic measurements revealed both Mn²⁺ and Mn³⁺ valence states as simultaneously present in the vitreous matrix and these ions are involved in negative superexchange interactions, being antiferromagnetically coupled.

Influence of Ni¹¹⁺ swift heavy ion (SHI) irradiation induced modifications on structural and morphological aspects of CuFe₂O₄ nanoparticles have been studied. The bulk sample is synthesized using co-precipitation technique. The cubic spinel structure is identified using X-ray diffraction technique and these nanoparticles have an average grain size of about 10 nm. These materials are irradiated at various fluences of 1 × 10¹¹, 1 × 10¹², 1 × 10¹³, 1 × 10¹⁴, and 5 × 10¹⁴ions/cm² using Ni¹¹⁺ ion beam of 150 MeV energy. The XRD pattern of the irradiated material shows the change in crystalline nature. The spinel ferrite (311) peak, which is having maximum intensity in the pristine, decreases at the fluence of 1 × 10¹¹ and 1 × 10¹²ions/cm² and then completely vanishes on further irradiation. However, a new X-ray peak arises in the (222) direction. All the other peaks in the pristine sample vanish on irradiation elucidating the creation of amorphization nature. Scanning electron microscope (SEM) analysis shows fine blocks of material for pristine and partial agglomeration on irradiation. Notably, a large number of holes are present at the fluence of 5 × 10¹⁴ions/cm² due to heavy ion irradiation. The phase change from crystalline to amorphous nature on XRD and the creation of holes from SEM is discussed on the basis of electrophonon coupling and it invokes the thermal spike theory.