Evidence of domain wall pinning in aluminum substituted cobalt ferrites

• Synthesis and characterization of CoAlxFe2−xO4 (x=0.0 to 0.3) ferrites.
• Experimental evidence of domain wall pinning.
• Analysis of magnetic, micro-structural, structural and spectroscopic data.
• Co-relation of the data obtained using various techniques with pinning effect.

In the present work spinel structured cobalt ferrites with aluminum substitution having composition CoAlxFe2−xO4 (x=0.0, 0.1, 0.2 and 0.3) have been synthesized using chemical co-precipitation method. Their microstructural, magnetic, magnetostriction and magnetoimpedance properties have been investigated. The piezomagnetic coefficient (dλ/dH) obtained from magnetostriction data is found to enhance with 0.1 Al substitutions in place of iron which decreases with further increase of Al content. It is noticed that 0.3 Al substitutions in place of Fe introduces domain wall pinning as evidenced from magnetostriction, magnetoimpedance and dc magnetization data. It is noted that ferrites so prepared using a simple procedure are magnetostrictive in good measure and with the addition of very small amount of non-magnetic aluminum their magnetostriction has shown saturation at relatively low magnetic fields. Such magnetostrictive ferrites find their applications in magnetic sensors and actuators.