VP19-01 Room temperature magnetodielectric studies of Sr3-xLaxCo2Fe24O41 hexaferrite
Creators: Anupriya Choudhary
Puneet Sharma
Bhupendra Chudasama
Publisher: name: IEEE
Year: 2025

Strontium Z-type hexaferrites (Sr3Co2Fe24O41) have received significant interest owing to their high permeability (μ) and permittivity (ε) making them suitable candidates for use in antenna miniaturization, multilayer chip inductors and other electronic devices for telecommunication applications. Recently, Z-type hexaferrites have attracted much attention for magnetodielectric (MD) effect at room temperature (RT), which is ascribed to transverse conical spin structure and spin-phonon coupling. Any disorder at regular Sr or Fe/Co sites may affect them. In the present study, La3+ ions were substituted for Sr2+ ions to induce two-fold effect, i.e different ionic radii and ion valency may disturb the conical spin structure and spin-phonon coupling. In the present work, La3+ substituted Sr3-xLaxCo2Fe24O41 (x = 0.0 and 0.20) hexaferrite were prepared by solid-state reaction method and their magnetodielectric properties were investigated. Z-type hexaferrite was formed as major phase with some minor impurity phases of M and W phases (Fig 1). Both saturation magnetization (Ms) and coercivity (Hc) increases with La content. The increase in Ms was attributed to the reduction of Fe3+ to Fe2+ at antiparallel 2a sites, whereas grain size reduction led to slight increase in Hc. FESEM micrographs showed densely packed hexagonal platelet-like structures with smaller grain size (~ 1.74 µm). The highest MD of 4.5% was observed at low frequency (100 Hz), which decrease with increase in frequency followed by a rapid increase at higher frequency (Fig 2). The large MD effect at low frequency is due to Maxwell-Wagner type Magnetoresistance (MR) effect whereas inverse Dzyaloshinskii–Moriya (DM) interaction induced spin phonon coupling is the dominant mechanism at high frequencies.
Strontium Z-type hexaferrites (Sr3Co2Fe24O41) have received significant interest owing to their high permeability (μ) and permittivity (ε) making them suitable candidates for use in antenna miniaturization, multilayer chip inductors and other electronic devices for telecommunication applications. Recently, Z-type hexaferrites have attracted much attention for magnetodielectric (MD) effect at room temperature (RT), which is ascribed to transverse conical spin structure and spin-phonon coupling. Any disorder at regular Sr or Fe/Co sites may affect them. In the present study, La3+ ions were substituted for Sr2+ ions to induce two-fold effect, i.e different ionic radii and ion valency may disturb the conical spin structure and spin-phonon coupling. In the present work, La3+ substituted Sr3-xLaxCo2Fe24O41 (x = 0.0 and 0.20) hexaferrite were prepared by solid-state reaction method and their magnetodielectric properties were investigated. Z-type hexaferrite was formed as major phase with some minor impurity phases of M and W phases (Fig 1). Both saturation magnetization (Ms) and coercivity (Hc) increases with La content. The increase in Ms was attributed to the reduction of Fe3+ to Fe2+ at antiparallel 2a sites, whereas grain size reduction led to slight increase in Hc. FESEM micrographs showed densely packed hexagonal platelet-like structures with smaller grain size (~ 1.74 µm). The highest MD of 4.5% was observed at low frequency (100 Hz), which decrease with increase in frequency followed by a rapid increase at higher frequency (Fig 2). The large MD effect at low frequency is due to Maxwell-Wagner type Magnetoresistance (MR) effect whereas inverse Dzyaloshinskii–Moriya (DM) interaction induced spin phonon coupling is the dominant mechanism at high frequencies.