Magnetic Properties of Sr Substituted Y-Type Hexaferrite

With the recent advances in high frequency antennas and RF devices requiring miniaturization, broad bandwidth, and impedance matching, magnetic material such as hexaferrites with high resonance frequency have been studied extensively. Here, we synthesized the Y-type hexaferrites (Ba_2-xSr_xCo_2-yZn_yFe₁₂O₂₂) by solid state reaction method and investigated their crystalline and magnetic properties by XRD, VSM, Mössbauer spectrometer and network analyzer. XRD patterns show that Ba_2-xSr_xCo_2-yZn_yFe₁₂O₂₂ samples have rhombohedral structures with space group R-3m. The VSM measurements show that the Zn substitution decreases the Néel temperature significantly while the Sr substitution does not. However, the spin reorientation temperature, corresponding to non-collinear helical to collinear ferrimagnetic transition, of Ba_2-xSr_xCo_2-yZn_yFe₁₂O₂₂ increased with Sr concentration. Complex permeability and permittivity of Ba_2-xSr_xCo_2-yZn_yFe₁₂O₂₂ samples were measured by network analyzer between 100 MHz to 4 GHz. Our study shows that the permeability of Ba_2-xSr_xCo_2-yZn_yFe₁₂O₂₂ (x = 0, y = 0.4) sintered at 1100°C is 2.38 at 2.45 GHz with tan δ_μ ≤ 0.1. Our experimental observation shows the potential application of Ba_2-xSr_xCo_2-yFe₁₂O₂₂ in RF devices in UHF band.