Browsing by Author "Valente-Rodrigues, C.L."

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    Investigation of Cr3+ doped Zn-Co nanoferrites as potential candidate for self-regulated magnetic hyperthermia applications
    (Institute of Physics, 2023-07-27T00:00:00) Valente-Rodrigues, C.L.; Caraballo-Vivas, Richard J; Santos, Evelyn C S; Sharma, Surender K; Garcia, Fl�vio
    Controlling the Curie temperature (TC) in the range from 42 �C-46 �C in magnetic hyperthermia (MH) therapy is an essential research topic because overheating can cause irreversible damage to healthy tissue. When TC is in the above temperature range, the magnetic nanoparticles reach a paramagnetic state, effectively turning off the MH treatment. In this work, we synthesized Zn-Co nanoparticles of representative composition Zn0.54Co0.46CrxFe2-xO4, where the Fe3+ cations are carefully replaced by Cr3+ ions, which allow a precise tuning of TC and hence the self-regulation of MH. The x-ray diffraction analysis of the prepared nanoparticles confirms the formation of a single-phase cubic spinel structure. The average crystallite of the nanoparticles increases with Cr3+ doping, while the Tc and saturation magnetization decrease considerably from 78 �C (x = 0.1) to 27 �C (x = 0.6) and 46.6 emu g?1 (x = 0.1) to 15.3 emu g?1 (x = 0.6), respectively. Besides MH potential of the investigated samples as revealed from specific absorption rate (SAR) assays and the maximum temperature reach (Tmax), vary from 7 W g?1 and 37.3 �C, for x = 0.6, to 38 W g?1 and 62.9 �C, for x = 0.1, we found that the composition Zn0.54Co0.46Cr0.4Fe1.6O4 is more promising with SAR of 22 W g?1 and Tmax = 42.3 �C, which is precisely lies in the safe temperature range to automatically activate the self-regulation during the magnetic hyperthermia treatment. The results reveal an excellent combination between size distribution and Cr3+ content in Zn-Co-based ferrite, which has a great potential for self-regulated magnetic hyperthermia applications. � 2023 IOP Publishing Ltd
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    Strain-mediated magnetoelectricity probed by Raman spectroscopy in h-ErMn O3
    (American Physical Society, 2023-07-05T00:00:00) Correa, A.; Barbosa, D.A.B.; De Menezes, A.S.; Valente-Rodrigues, C.L.; Sharma, Surender Kumar; Santos, C.C.
    We show the role of strain in magnetoelectric effect through coupling between order parameters and their interplay using infrared/Raman-active optical phonons in hexagonal manganite (h-ErMnO3). The magnetoelectric coupling is arbitrated through strain from infrared-active phonons, which by symmetry are also Raman active. The identification of the primitive order parameters by spin-phonon coupling opens a promising avenue to realize the strategy based on coupling of spins, optical phonons, and strain to create magnetoelectrics with strain-mediated interaction through spin-lattice coupling in bulk inducing a ferromagnetic-ferroelectric state in an antiferromagnetic-paraelectric phase. � 2023 American Physical Society.