Nd-Co substituted strontium hexaferrite powders: Microwave absorbing properties in the X-band

C. HERME; P. G. BERCOFF; S. E. JACOBO

Buenos Aires

Workshop; X Latin American Workshop on Magnetism and Magnetic Materials (X-LAW3M); 2013

The increasing exploitation of microwave (MW) frequencies for telecommunication purposes has increased the amount of interference and EM pollution and stimulated the development of MW absorbers. The absorption of EM waves in magnetic materials is due to their magnetic losses. By varying the chemical composition it is possible to control properties such as saturation magnetization, magnetocrystalline anisotropy, coercivity, and permeability and permittivity of a ferrite composite. In this work we report the MW absorbing behaviour of Nd-Co substituted strontium hexaferrite powders. Particles of composition Sr1-xNdxFe11-xCoxO19 with an average size of 200 nm were prepared by the self combustion method with further heat treatment at 1100ºC. Structural characterization of these samples was carried out by XRD, SEM and hysteresis loops, M vs H. Powders of ferrite without doping and Nd-Co doped (x = 0.2) were mixed with epoxy resin and measured using a VNA over the X-band range (7-13 GHz). Transmission and reflection coefficients were determined to evaluate the absorbing properties of these materials. Complex permittivity and permeability spectra were calculated by the Nicolson-Ross-Weir conversion method. Significant reflection loss values were achieved by the ferrites between 9.5 and 12.5 GHz with a sample thickness of 4 mm.