The Effect of Thickness‐Tunable ZrO₂ Shell on Enhancing the Tunneling Magnetoresistance of Fe₃O₄ Supraparticles

Abstract The core–shell Fe₃O₄@ZrO₂ nanoparticles with controllable shell thickness and core dimensions are synthesized using solvothermal approaches. The introduction of the insulator ZrO₂ shell allows realizing the enhancement of tunneling magnetoresistance (TMR) effect of the functional nanomaterials. The influences of temperature, magnetic field, and shell thickness on the TMR are explored. With the shell thickness ≈3 nm TMR ratio of 10% is obtained, which improves the MR compared to the pure Fe₃O₄ counterpart of 5.7%. Furthermore, the MR is increased first and then decreases with increase of the shell thickness, which suggests that the addition of insulated shell‐layer promotes the electron tunneling among the supraparticles and thereby increases the MR. The fault‐cutting data indicate that the tunneling mechanism occurs mainly through the magnetic‐insulator interfaces rather than the interior nanoparticle interfaces. In addition, the MR with different core‐size presents a monotonic increase with decrease of the size of core.