Bulk magnetite (Fe3O4), the loadstone used in magneticcompasses, has been known to exhibit magnetoelectric (ME) propertiesbelow-10 K;however, correspondingME effects in Fe3O4nanoparticles havebeen enigmatic.We investigate quantitatively the ME coupling ofspherical Fe3O4nanoparticleswith uniform diameters (d) from 3 to 15 nmembedded in an insulating host, usingasensitive ME susceptometer. The intrinsic ME susceptibility (MES)of the Fe3O4nanoparticlesis measured, exhibiting amaximum value of -0.6 ps/m at 5 K for d=15 nm. We found that the MESis reducedwith reduceddbut remains finite untild=-5nm, which is close to the critical thickness for observingtheVerwey transition. Moreover,with reduced diameter,the critical temperature below which the MES becomes conspicuous increased systematically from 9.8 K in the bulk to 19.7 K in the nanoparticles with d=7 nm, reflecting the core-shell effect on the ME properties. These results point to a new pathway for investigating ME effect in various nanomaterials.
|Publication status||Published - 2017 Sep 1|
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