IMF2017

Hexagonal ferrites attracted recently great attention as candidates for microwave absorbers due to low electric conductivity and low eddy current losses. Moreover, doping and codoping can be used to study the exchange coupling and to adjust intrinsic and extrinsic magnetic properties of the ferrites to application requirements. We studied the magnetic and dielectric response of Sr_0.95Nd_0.05Fe_12-xAl_xO₁₉ ( x = 0.36, 0.60, 0.84 and 1.08) obtained by hydrothermal synthesis. Single phase solid solution with P6₃/mmc space group and Z = 2 has been confirmed for all samples by X-ray diffraction and the lattice parameters were unaffected by Al³⁺ doping. SEM images revealed that the samples consist of 10-20 nm thick agglomerated platelets. Magnetic studies showed that the codoping influences mainly the intrinsic magnetic properties. Analysis of the Al³⁺ induced changes in the magnetic properties points to the substitution of Fe³⁺ ions in octahedral 4f₂ Wyckoff positions. Temperature variation of the magnetization M_ZFC in zero-field-cooled and M_FC in field-cooled experiments revealed a bifurcation and a maximum in M_ZFC(T) dependences. The temperature of the maximum was found to be shifted towards higher temperatures with increasing x and we propose to relate the feature to cluster-glass-like behavior. The dielectric permittivity and electric conductivity measurements in the frequency range 1Hz – 1GHz show that the dielectric response of the solid solution can be described within the Koops model.