Colossal piezomagnetic response in magnetically pressed Zr+4 substituted cobalt ferrites

Abstract A remarkable 111% increase in magnetostriction (λ) and 435% increase in strain sensitivity (d λ /d H ) (compared to normally compacted (NC) unsubstituted CoFe 2 O 4 (CFO)) of Zr +4 doped CFO sample, Co 1.2 Zr 0.2 Fe 1.6 O 4 , prepared by magnetic field assisted compaction, have been reported in this study. Magnetic field assisted compaction (MC) has been employed to process Zr-doped cobalt ferrites, Co 1+x Zr x Fe 2−2x O 4 (0 ≤ × ≤ 0.4), to further improve the magnetoelastic properties. Saturation magnetization ( M S ) and coercivity ( H C ) increase from ~426 kA/m and ~4.4 kA/m respectively, for x = 0, to ~552 kA/m and ~7.11 kA/m respectively for x = 0.2. Dramatic increase in λ was observed for MC samples (~ −360 ppm and ~−380 ppm for x = 0 and x = 0.2 respectively) compared to the NC samples (~−181 ppm and ~−185 ppm for x = 0 and x = 0.2 respectively). A remarkable quadruple increase in d λ /d H was observed in Zr-doped ( x = 0.2) cobalt-ferrite (~4.3 × 10 −9 A −1 m) compared to that of unsubstituted cobalt-ferrite (~1.24 × 10 −9 A −1 m), while a fivefold increase in d λ /d H was observed for magnetically compacted (MC) Zr doped cobalt ferrite ( x = 0.2) (~4.3 × 10 −9 A −1 m) compared to normal compacted (NC) unsubstituted cobalt ferrite (~0.8 × 10 −9 A −1 m).