Effect of Aliovalent Substitution in Y2.9Bi0.1Fe₅O₁₂: Magnetization Dynamic Study

Multifunctional multiferroic materials, such as rare-earth-doped yttrium iron garnet (YIG), are advantageous for low-energyconsumption devices. In this work, we investigated aliovalent (Ce
⁴⁺
) substitution in Y
_2.9
Bi
_0.1
Fe
₅
O
₁₂
ferrite with different compositions Y
_2.9-x
Ce
_x
Bi
_0.1
Fe
₅
O
₁₂
(x = 0.0, 0.2, 0.4), respectively. The ferrites were fabricated by a conventional solid-state reaction method, and their structural, static, and dynamic magnetic properties were studied at room temperature. The X-ray diffraction (XRD) pattern confirmed the Ia3̅d cubic phase of all the ferrite compositions together with ceric oxide (CeO
₂
) as a residual phase containing aliovalent ions. The lattice parameter “a” of synthetic garnets decreases linearly with Ce concentration. From the static magnetic measurements, we observed that the saturation magnetization (4πMS) decreases due to combined effect of Ce
³⁺
paramagnetic ions and Ce
⁴⁺
diamagnetic aliovalent ions. Magnetization dynamics have been studied by ferromagnetic resonance (FMR) technique in flip-chip geometry on the coplanar waveguide. Field sweep FMR spectra revealed that the microwave absorption in the X-band and the Ku-band decreases with Ce concentration due to a decrease in the super-exchange interaction between Fe ions at [a] and (d) sites due to electronic transition of Ce
³⁺
ion. A major investigation of this study shows a decrease in the Gilbert damping constant (α) from 1.6 × 10
^-3
to 1.52 × 10
^-3
and increase in extrinsic contribution Δ(H
_o
) to the FMR linewidth A(H) from 0.38 to 0.54 kOe with Ce concentration. Therefore, this investigation opens a door for the next generation magneto-electric, magneto-optic, and magneto-dielectric effect-based spintronics/magnonics devices in the microwave regime.