Magnetite (Fe₃O₄) Core−Shell Nanowires:  Synthesis and Magnetoresistance

Abstract

High quality MgO/Fe 3 O 4 core−shell nanowires have been successfully synthesized by depositing an epitaxial shell of Fe 3 O 4 onto single crystal MgO nanowires. The material composition and stoichoimetric ratio have been carefully examined and confirmed with a variety of characterization techniques. These novel structures have rendered unique opportunities to investigate the transport behavior and spintronic property of Fe 3 O 4 in its one-dimensional form. Room-temperature magnetoresistance of ∼1.2% was observed in the as-synthesized nanowires under a magnetic field of B ) 1.8 T, which has been attributed to the tunneling of spin-polarized electrons across the anti-phase boundaries.

Magnetoresistance characteristics in individual Fe3O4 single crystal nanowire

“…The circles represent resistance (R) data points acquired from original I-V scans and the line represents best fit. Electrical resistance of single Fe 3 O 4 nanowire at room temperature is around 5 Â 10 À4 X m, which is comparable to epitaxial thin films 14,25 and higher than bulk single crystal Fe 3 O 4 . 26 Electrical resistance below 120 K is almost 2 orders of magnitude higher compared to room temperature.…”

“…Epitaxially grown MgO/Fe 3 O 4 core shell nanostructures were found to have 1.2% MR at room temperature under 1.8 T applied field, which is credited to the tunneling of spin-polarized electrons across the antiphase boundaries. 14 Terrier et al measured the transport properties of several polycrystalline nanowires and reported 8.5% MR at room temperature and did not observe any anisotropy. 15 The magneto-electron transport properties of an individual single crystalline Fe 3 O 4 nanowire are still inconsistent.…”

“…16 But, unusual positive MR 16 observation in single crystal nanowire is contradicting the negative MR observed with epitaxial thin films, bulk and polycrystalline Fe 3 O 4 . 2,4,14,17,18 In this report, we discuss the magneto-electron transport properties from a single crystalline magnetite nanowire that exhibits negative MR. Single crystal Fe 3 O 4 nanowires were prepared by a simple hydrothermal method.…”

Heterojunction metal-oxide-metal Au-Fe3O4-Au single nanowire device for spintronics

“…[1][2][3][4][5] Multifunctional magnetic nanowires (metal or oxide) have received much attention due to their potential application in perpendicular data recording, spintronics devices, scanning tips in magnetic force microscope, and in other biological applications. [6][7][8][9][10][11] Among them, magnetite (Fe 3 O 4 ) have garnered much consideration for magnetoresistance 12,13 and spin filter device applications. 14 Magnetite has been the subject of extensive research efforts because of high spin polarization and above room temperature Curie temperature, which finds applications in magneto-electronics.…”

“…A room temperature ferromagnet with 858 K curie temperature and 100% spin polarization at the Fermi level with majority spin electrons exhibiting insulating or semiconducting behavior while the minority spins showing the metallic behavior has rendered the Fe 3 O 4 to be obvious choice for magneto-electronics. 15 Spin polarization or magneto-electronic measurements on Fe 3 O 4 were probed through electrical contacts to the oxide via evaporated metal electrodes, 12 or via spin-polarized electron spectroscopy, 16 or electron holography. 17 Magnitude of the spin polarized current was found to depend on material microstructure, grain size, grain boundary, defects, strain effects, and surface/interface reconstruction.…”