Enabling cobalt ferrite (CoFe2O4) for low magnetic field strain responsivity through Bi3+ substitution: material for magnetostrictive sensors

Abstract Bismuth-substituted cobalt ferrite, CoBixFe2-xO4 (x=0, 0.1, 0.2 and 0.3), samples with enhanced magnetostriction behaviour were synthesized through a glycine-nitrate based auto-combustion route. The powders were pelletized and sintered at 1450 °C for 10 min. The presence of Bi3+ in CoFe2O4 promotes a significant grain growth. The samples with x=0 and 0.1 are found to be phase pure with cubic spinel structure, whereas a secondary phase (Bi2O3) starts forming beyond this composition due to the low solubility limit of Bi3+ in cobalt ferrite. According to our results, the maximum strain sensitivity (dλ/dH)max for Bi-doped samples (~ -1.6×10-9 m/A) is considerably higher than that of the parent compound (~ -1×10-9 m/A) even at lower magnetic-fields. Our work demonstrates the strategy to enhance the strain sensitivity of magnetostrictive sensors at lower applied magnetic fields through sintering of Co-ferrite samples after Bi3+ doping.