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at room temperature. This degradation is caused admittedly by the reduced spin polarization due to the multiple effects of oxidation, defects, bonding, and surface reconstruction at the surfaces or interfaces of the polycrystal grain boundaries. Comparing to bulk materials, the nanoparticles can produce enhanced extrinsic MR owing to the effect of spin-dependent interface scattering or tunneling through the boundaries. [18] Additionally, the MR can still be increased by core-shell encapsulated structures. For example, an insulating shell coats on the magnetite core. In such a dielectric system, nanometric ferromagnetic particles show giant TMR by spin-dependent tunneling of conducting electrons at the magneticinsulator interfaces. Electrons with spin parallel to the particle magnetization have a bigger probability of tunneling than electrons with antiparallel spin, resulting in an overall lower resistance. Similar MR enhancement has been realized in Fe 3 O 4 @SiO 2 , [19] Fe 3 O 4 @ oleic acid, [20] Fe@Cr, [21] and Fe 3 O 4 @ZnS [22] system. Insulator zirconium dioxide (ZrO 2 ) is a nonmetallic inorganic material and has excellent resistance to acids and alkalis. It was widely applied in catalyst carrier and thermal barrier fields due to the stability and insulativity. Previous studies have shown that ZrO 2 doping in the perovskite systems can effectively enhance the magnetoresistance. [23][24][25] To the best of our knowledge, it is still unexploited of ZrO 2 doping in the half-metal Fe 3 O 4 nanoparticles by means of the core-shell structural system.In this paper, Fe 3 O 4 @ZrO 2 core-shell nanocomposites are prepared with controllable shell thickness and core-size. The pomegranate-like core is obtained and composed of several monocrystals and single-domain Fe 3 O 4 nanocrystals with size <10 nm. The magnetic structure and magnetotransport property of the core-shell nanocomposites are explored. Our results show that the MR is increased to ≈7.5% at 2 kOe in this core-shell system compared to that of pure Fe 3 O 4 nanoparticles ≈4.7%. Moreover, as Zr content increases, the MR first increases and then decreases. This is because the addition of insulated barrier promotes the tunneling effect, which enhances the MR, but with further increase of ZrO 2 thickness, the barrier becomes larger and the electron tunneling becomes difficult, leading to the reduced MR. In addition, the results of Fe 3 O 4 @ZrO 2 with different core sizes show that the MR rises monotonically with a decrease of the size of core. Moreover, for eliminate the possible effect of ZrO 2 permeating into the interior of the pomegranate-like core, fault-cutting is prepared andThe core-shell Fe 3 O 4 @ZrO 2 nanoparticles with controllable shell thickness and core dimensions are synthesized using solvothermal approaches. The introduction of the insulator ZrO 2 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 ...
at room temperature. This degradation is caused admittedly by the reduced spin polarization due to the multiple effects of oxidation, defects, bonding, and surface reconstruction at the surfaces or interfaces of the polycrystal grain boundaries. Comparing to bulk materials, the nanoparticles can produce enhanced extrinsic MR owing to the effect of spin-dependent interface scattering or tunneling through the boundaries. [18] Additionally, the MR can still be increased by core-shell encapsulated structures. For example, an insulating shell coats on the magnetite core. In such a dielectric system, nanometric ferromagnetic particles show giant TMR by spin-dependent tunneling of conducting electrons at the magneticinsulator interfaces. Electrons with spin parallel to the particle magnetization have a bigger probability of tunneling than electrons with antiparallel spin, resulting in an overall lower resistance. Similar MR enhancement has been realized in Fe 3 O 4 @SiO 2 , [19] Fe 3 O 4 @ oleic acid, [20] Fe@Cr, [21] and Fe 3 O 4 @ZnS [22] system. Insulator zirconium dioxide (ZrO 2 ) is a nonmetallic inorganic material and has excellent resistance to acids and alkalis. It was widely applied in catalyst carrier and thermal barrier fields due to the stability and insulativity. Previous studies have shown that ZrO 2 doping in the perovskite systems can effectively enhance the magnetoresistance. [23][24][25] To the best of our knowledge, it is still unexploited of ZrO 2 doping in the half-metal Fe 3 O 4 nanoparticles by means of the core-shell structural system.In this paper, Fe 3 O 4 @ZrO 2 core-shell nanocomposites are prepared with controllable shell thickness and core-size. The pomegranate-like core is obtained and composed of several monocrystals and single-domain Fe 3 O 4 nanocrystals with size <10 nm. The magnetic structure and magnetotransport property of the core-shell nanocomposites are explored. Our results show that the MR is increased to ≈7.5% at 2 kOe in this core-shell system compared to that of pure Fe 3 O 4 nanoparticles ≈4.7%. Moreover, as Zr content increases, the MR first increases and then decreases. This is because the addition of insulated barrier promotes the tunneling effect, which enhances the MR, but with further increase of ZrO 2 thickness, the barrier becomes larger and the electron tunneling becomes difficult, leading to the reduced MR. In addition, the results of Fe 3 O 4 @ZrO 2 with different core sizes show that the MR rises monotonically with a decrease of the size of core. Moreover, for eliminate the possible effect of ZrO 2 permeating into the interior of the pomegranate-like core, fault-cutting is prepared andThe core-shell Fe 3 O 4 @ZrO 2 nanoparticles with controllable shell thickness and core dimensions are synthesized using solvothermal approaches. The introduction of the insulator ZrO 2 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 ...
Both surface and interface scattering induced a sign reversal of anomalous Hall effects (AHE) in a few heterostructures. The sign reversal exiting in a single-substance can clarify the role of...
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