UltrathinFe3O4epitaxial films on wide bandgap GaN(0001)

Abstract

Ultrathin films of magnetite ͑Fe 3 O 4 ͒ have been grown epitaxially on wurtzite wide bandgap semiconductor GaN͑0001͒ surfaces using molecular-beam epitaxy. Reflection high-energy electron-diffraction patterns show a ͑111͒ orientation of the Fe 3 O 4 films and in-plane epitaxial relationship of ͗110͘ Fe 3 O 4 ʈ ͗1120͘ GaN and ͗112͘ Fe 3 O 4 ʈ ͗1100͘ GaN with the GaN͑0001͒. X-ray photoelectron spectroscopy and x-ray magnetic circular dichroism confirm the growth of stoichiometric Fe 3 O 4 , instead of ␥ -Fe 2 O 3 . The magnetic hysteresis loops and saturation magnetization M s obtained by superconducting quantum interference device at room temperature show fast saturation of the Fe 3 O 4 films with the magnetization close to that of the bulk single-crystal value. In-plane magnetoresistance ͑MR͒ measurements reveal negligibly small MR effects, further indicating that the films are free from antiphase boundaries.

Magnetism in nanometer-thick magnetite

“…[23][24][25][26][27][28] Here we examine the presence of stable ferrimagnetic domains in ultrathin magnetite, a subject with conflicting reports in the literature. While some reports state than magnetite films close to 3 nm thick present a well defined magnetic structure, 20,22,23,29,30 others indicate that clear signs of superparamagnetic behavior are observed at the same thickness. 12,[31][32][33][34] We grow 1-nm-thick, micron-wide, magnetite crystals on ruthenium 25 using reactive molecular beam epitaxy (i.e., depositing iron in a background of oxygen) while monitoring the growth in real time by low-energy electron microscopy (LEEM 27 ).…”

“…9 Oxides like magnetite have much more complicated structures and larger unit cells than metal ferromagnets, giving the possibility of tuning their properties to a larger extent, especially given the often observed strong coupling to strain effects. 10,11 Magnetite ultrathin nanostructures have been grown on a variety of substrates, including oxides, [12][13][14][15][16][17][18] semiconductors, [18][19][20][21][22] and metals. [23][24][25][26][27][28] Here we examine the presence of stable ferrimagnetic domains in ultrathin magnetite, a subject with conflicting reports in the literature.…”

Hybridization-induced charge rebalancing at the weakly interactive C60/Fe3O4(001) spinterface

“…Both first-and half-order diffraction spots on a cubic plane are clearly observed, thus indicating the expected inverse spinel structure of Fe 3 O 4 . On the other hand, being a mixed-valence material with a well-defined Fe 3þ / Fe 2þ ion distribution, the stoichiometry and oxidation state of Fe 3 O 4 can be further confirmed by XMCD [22][23][24][25]. Fig.…”

Inverse magnetoresistance in textured Fe3O4 film

“…XMCD is the difference of the absorption intensities by reversing helicity of the incoming circularly polarized x-ray [16e18]. The ferrimagnetic multiplet structure of the Fe L 2,3 XAS and XMCD spectra features contributions from the Fe 3þ cations at tetrahedral sites and both Fe 2þ and Fe 3þ cations at octahedral sites [19], showing a good agreement with stoichiometric Fe 3 O 4 . This is different from the case of g-Fe 2 O 3 , where the peak corresponding to octahedral Fe 2þ would be strongly suppressed [20,21], and provides direct evidence for the formation of Fe 3 O 4 with a quality close to that of the bulk.…”