Mossbauer Spectroscopic Study of High Magnetostrictive Cobalt Chromium Ferrites for Automobile Torque Sensors

Abstract

Co-Cr ferrites with the chemical formulae, CoFe2-xCrxO4 (x = 0 to 0.5 in steps of 0.1) were prepared by sol gel autocombustion method. Lattice constants were determined from X-ray diffraction patterns. Magnetic properties were studied by VSM and Mössbauer spectroscopy. Magnetostrictive coefficients were measured using strain gauge technique. The magnetostriction coefficient has been observed to increase sharply at higher chromium concentrations (x = 0.3 - 0.5). The hyperfine field Hhf values at B- and A-sites showed an initial increase at both the sites followed by a gradual monotonic decrease with increasing chromium ion concentration (x). The Fe3+ (B)/Fe3+ (A) ratio obtained from the Mössbauer spectra decreases with increasing chromium concentration. The results have been explained on the basis of super transferred hyperfine fields.