Microwave absorption studies of (Ba0.5Sr0.5Fe12O19)1-x/(NiFe2O4)x hard/soft ferrite nanocomposites

Abstract

Magnetic nanocomposites consisting of barium strontium hexaferrite and nickel ferrite as the hard and the soft phases respectively (Ba0.5Sr0.5Fe12O19)1-x/(NiFe2O4)x with the compositions x = 0.1, 0.2, 0.3 and 0.4, were synthesized by a modified sol-gel technique using citric acid as the fuel. The as-synthesized material was heat treated at 1100 °C for 2 h. A 20% increase in the Ms was found in the ferrite nanocomposite with the addition of 10 wt% of NiFe2O4. Decrease in coercive field with increase in soft phase content was observed, attributing to the dominance of dipolar interaction over exchange interaction. There was no kink observed in the hysteresis loops of nanocomposites, confirming the single-phase behaviour. All the nanocomposites prepared by the modified sol-gel method exhibited good exchange coupling behaviour with Mr/Ms values of >0.5. All the prepared nanocomposites displayed excellent microwave absorption properties in the X-band region (8–12 GHz). The absorber thickness was maintained as 2.5 mm. Minimum reflection loss of −38.74 dB was attained for the composition (Ba0.5Sr0.5Fe12O19)0.6/(NiFe2O4)0.4, which is 47% higher than the pure Ba0.5Sr0.5Fe12O19.