@Article{DhruvMPCJBPMRB:2020:InStMa,
               author = "Dhruv, Preksha N. and Meena, Sher Singh and Pullar, Robert C. and 
                         Carvalho, Francisco E. and Jotania, Rajshree B. and Bhatt, Pramod 
                         and Prajapat, C. L. and Machado, Jo{\~a}o Paulo Barros and Rao, 
                         T. V. Chandrasekhar and Basak, C. B.",
          affiliation = "{Gujarat University} and {Bhabha Atomic Research Centre} and 
                         {University of Aveiro} and {Instituto Tecnol{\'o}gico de 
                         Aeron{\'a}utica (ITA)} and {Gujarat University} and {Bhabha 
                         Atomic Research Centre} and {Bhabha Atomic Research Centre} and 
                         {Instituto Nacional de Pesquisas Espaciais (INPE)} and {Bhabha 
                         Atomic Research Centre} and {Homi Bhabha National Institute}",
                title = "Investigation of structural, magnetic and dielectric properties of 
                         gallium substituted Z-type Sr3Co2-xGaxFe24O41 hexaferrites for 
                         microwave absorbers",
              journal = "Journal of Alloys and Compounds",
                 year = "2020",
               volume = "822",
                pages = "e153470",
                month = "may",
             keywords = "Gallium substituted Z-type hexaferrites, Sol-gel auto-combustion, 
                         Structural properties, Magnetic properties, Microwave absorption 
                         performance.",
             abstract = "Gallium substituted Z-type hexagonal ferrites with chemical 
                         composition Sr3Co2-xGaxFe24O41 (x ¼ 0.0,0.4, 0.8, 1.2, 1.6, and 
                         2.0) were successfully synthesised in air at 1200 C for 5 h using 
                         the sol-gel autocombustion technique, in order to investigate the 
                         effect of gallium substitution on structural, magnetic and 
                         dielectric properties. X-ray Diffraction (XRD) analysis of all 
                         samples reveals the formation of mixed hexaferrite phases, with Z 
                         ferrite as the major phase (72e90%).The average crystallite size 
                         of heated powders was found to be in the range of 21e40 nm. The 
                         saturation magnetisation decreases after gallium substitution, 
                         with the lowest values of 64 Am2 kg1 for composition x ¼ 1.6, 
                         which also hasthe highest value of coercivity (28.3 kA m1 ). 
                         Nevertheless, all were soft ferrites, with Hc between 3.4 and 28.3 
                         kA m1 .The Mr/MS ratio of all samples was found to be less than 
                         0.5, suggesting that all the compositions possess multi-domain 
                         microstructures. Mossbauer spectroscopic analysis con firmed that 
                         the Fe ions were found in the 3 þ high spin state for compositions 
                         below x 0.4, whereas ~1.5% of the Fe ions were converted into Fe2þ 
                         high spin state beyond x 0.8 compositions, as Ga3þ began to 
                         substitute for Fe3þ, forming Fe2þ in the cobalt positions. The 
                         average hyperfine magnetic field (<Hhf>) was found to be decreased 
                         with Ga-substitution. Dielectric parameters such as dielectric 
                         constant and loss factor were studied as a function of frequency, 
                         and their results show normal behaviour for ferrimagnetic 
                         materials. In complex measurements at microwave frequencies (8 
                         GHze12.5 GHz, the X-band), all samples had a real permittivity of 
                         around 8e14. For sample x ¼ 2.0, a dielectric resonance peak was 
                         observed around 12.15 GHz. All showed a real permeability of 
                         around 1.0e1.4 over the frequency of 8 GHze12.5 GHz range, and 
                         ferromagnetic resonance (FMR) was observed in x ¼ 0.0 and 2.0 
                         samples, at around 11 and 12 GHz, respectively. This suggests that 
                         the prepared samples can be used as microwave absorbers/EMI 
                         shielding at specific microwave frequencies. The co-existence of 
                         FMR and dielectric resonance at the same frequency of 12.15 GHz 
                         for x ¼ 2.0 could lead to the coupling of these resonances and the 
                         development of potential metamaterials.",
                  doi = "10.1016/j.jallcom.2019.153470",
                  url = "http://dx.doi.org/10.1016/j.jallcom.2019.153470",
                 issn = "0925-8388",
             language = "en",
           targetfile = "dhruv_investigation.pdf",
        urlaccessdate = "27 abr. 2024"
}