Scale‐Enhanced Magnetism in Exfoliated Atomically Thin Magnetite Sheets

Abstract

It had been found that spinorbit coupling components were small in FeO systems, [44,45] therefore collinear spin model was used in the magnetene layers. The Brillouin zone integrations for the bulk and slab were carried out on a converged Monkhorst pack k-mesh of sizes 3 × 3 × 3 and 4 × 6 × 1, respectively.

Friction of magnetene, a non–van der Waals 2D material

“…Correspondingly, the magnetene O1s peak confirms this reduced valence showing a predominance of Fe 2+ -O, while the Fe 3+ -O peak is diminished. This indicates that, upon confinement, the collective valence state is reduced from the bulk Fe 2.48+ to Fe 2.19+ , which is in agreement with previous DFT calculations that showed a decrease from +1.25 |e| at the Fe octahedral site (mixed Fe 2+ and Fe 3+ ) to +1.1 |e| ( 7 ). The second predominant difference that can be noted by the XPS spectra is the O1s signal.…”

“…1, A, D, G, and H ) ( 6 ), magnetene (Fe 3 O 4 ; Fig. 1, B, E, H, and I ) ( 7 ), and chromiteen (FeCr 2 O 4 ; Fig. 1, C, F, I, and L ) ( 8 ) are 2D iron oxide nanomaterials that can be cleaved by liquid sonication exfoliation along their respective weak planes, producing uniform atomic layers.…”

“…The vast majority of 2D materials are produced by cleavage of weak van der Waals (vdW) bonds between layers. However, a series of non-vdW-bonded 2D materials from transition metal oxides have been recently exfoliated (6)(7)(8)(9)(10)(11)(12). Of particular note, the iron oxide materials including hematene (Fe 2 O 3 ), magnetene (Fe 3 O 4 ), and chromiteen (FeCr 2 O 4 ) are 2D versions of bulk ores, which present thicknesses down to a monolayer despite featuring covalent bonding out of plane (6)(7)(8).…”

“…However, a series of non-vdW-bonded 2D materials from transition metal oxides have been recently exfoliated (6)(7)(8)(9)(10)(11)(12). Of particular note, the iron oxide materials including hematene (Fe 2 O 3 ), magnetene (Fe 3 O 4 ), and chromiteen (FeCr 2 O 4 ) are 2D versions of bulk ores, which present thicknesses down to a monolayer despite featuring covalent bonding out of plane (6)(7)(8). These 2D materials have exhibited distinct magnetic and photocatalytic properties from their bulk counterparts due to preferred magnetic spin moments by planar confinement and increased bandgap by confined spin polarization, respectively (6)(7)(8).…”

Exfoliation of hematite: Morphological, structural and magnetic investigations

“…Recently, Balan et. al., reported that natural mineral specimens can be ultrasonically exfoliated in a solvent to yield ultra-thin sheets that they called 'hematene' [3] or 'magnetene' [4]. Other authors previously synthesised magnetic half-unit-cell thick α-Fe2O3 nanosheets from a goethite precursor, using template-assisted oriented growth [5].…”