Fortified relaxor ferroelectricity of rare earth substituted 4-layered BaBi3.9RE0.1Ti4O15 (RE = La, Pr, Nd, and Sm) Aurivillius compounds

Tirupathi, Patri; Ghosh, Avijit; Mahesh, M. L. V.; Babu, P. D.; Mandal, Subinay; Singh, M. N.

doi:10.1038/s41598-022-18855-9

Cited by 13 publications

(3 citation statements)

References 71 publications

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“…The exponent values n 1 and n 2 were plotted against temperature (Figure 6d). The frequency-independent conductivity at lower frequencies for all samples can be illustrated using the ion-jump relaxation model [73,74]. The defective ions, which were oxygen vacancies, hopped between their neighborhood vacant sites of Ti 3+ and Ti 4+ .…”

Section: Electrical Studiesmentioning

confidence: 99%

Magnetoelectric Properties of Aurivillius-Layered Perovskites

Veenachary,

Ramana,

Narendra Babu

et al. 2024

Crystals

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In the present work, we have synthesized rare-earth ion modified Bi4−xRExTi2Fe0.7Co0.3O12−δ (RE = Dy, Sm, La) multiferroic compounds by the conventional solid-state route. Analysis of X-ray diffraction by Rietveld refinement confirmed the formation of a polycrystalline orthorhombic phase. The morphological features revealed a non-uniform, randomly oriented, plate-like grain structure. The peaks evident in the Raman spectra closely corresponded to those of orthorhombic Aurivillius phases. Dielectric studies and impedance measurements were carried out. Asymmetric complex impedance spectra suggested the relaxation of charge carriers belonging to the non-Debye type and controlled by a thermally activated process. Temperature-dependent AC conductivity data showed a change of slope in the vicinity of the phase transition temperature of both magnetic and electrical coupling natures. Based on the universal law and its exponent nature, one can suppose that the conduction process is governed by a small polaron hopping mechanism but significant distortion of TiO6 octahedral. The doping of the A-sites with rare-earth element ions and changes in the concentrations of Fe and Co ions located on the B-sites manifested themselves in saturated magnetic hysteresis loops, indicating competitive interactions between ferroelectric and canted antiferromagnetic spins. The magnetic order in the samples is attributed to pair-wise interactions between adjacent Fe3+–O–Fe3+, Co2+/3+–O–Co3+/2+, and Co2+/3+–O–Fe3+ ions or Dzyaloshinskii–Moriya interactions among magnetic ions in the adjacent sub-lattices. As a result, enhanced magnetoelectric coefficients of 42.4 mV/cm-Oe, 30.3 mV/cm-Oe, and 21.6 mV/cm-Oe for Bi4−xDyxTi2Fe0.7Co0.3O12−δ (DBTFC), Bi4−xLaxTi2Fe0.7Co0.3O12−δ (LBTFC), and Bi4−xSmxTi2Fe0.7Co0.3O12−δ (SBTFC), respectively, have been obtained at lower magnetic fields (<3 kOe). The strong coupling of the Aurivillius compounds observed in this study is beneficial to future multiferroic applications.

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Section: Electrical Studiesmentioning

confidence: 99%

Magnetoelectric Properties of Aurivillius-Layered Perovskites

Veenachary,

Ramana,

Narendra Babu

et al. 2024

Crystals

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“…It is conceivable that the substitution of Ti 4+ by Fe 3+ and Mn 3+ could be accompanied by the formation of compensating oxygen vacancy defects (22,23). However,…”

Section: Ionic Compensation By Defectsmentioning

confidence: 99%

“…Another possible mechanism is ionic compensation by the introduction of ionic defects such as oxygen vacancies (21)(22)(23). Additionally, if the solubility limit is exceeded, segregation of impurity species or secondary phases at grain boundaries or at surfaces can occur (24)(25)(26).…”

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Charge compensation and structural adaptation to accommodate increased magnetic cation content in multiferroic Aurivillius phases

Halpin,

Schmidt,

Whatmore

et al. 2024

Preprint

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The five-layered (m = 5) Bi6Ti2.99Fe1.46Mn0.55O18 Aurivillius material is a rare example of a single-phase room temperature ferroelectric-ferromagnetic multiferroic that could ideally be suited to future energy-efficient memory devices. This study examines the effect of B-site substitution with the aim of increasing the proportion of magnetic ions within the structure and consequently increasing the saturation magnetisation. Four series of Aurivillius phase films with a target composition of Bi6TixFeyMnzO18 (B6TFMO; x = 2.3 to 3.2, y = 1.2 to 2.0, z = 0.3 to 0.9) were fabricated by chemical solution deposition. Substitution of Ti4+ by Fe3+ and Mn3+ necessitates charge compensation mechanisms and requires accommodation of differing ionic radii. While valence changes of Mn3+ to Mn4+ can act to compensate charge, XRD and TEM analysis is used here to demonstrate that above a threshold of 8 % nominal Mn4+, the m = 5 structure can no longer accommodate the smaller Mn4+ ion and it rearranges into a mixed-phase material based on m = 5 and six-layered (m = 6) inter-growths. Increasing the number of perovskite layers by forming the m = 6 structure facilitates the accommodation of additional magnetic cations at a lower average manganese oxidation state (+3.3). This work provides valuable insight into the design and development of versatile multiferroic phases by describing how the B-site magnetic cation content can be increased to 54 % in m = 6 structures, compared to a solubility limit of 46 % in m = 5 structures.

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