Role Of Antiphase Boundaries Research Articles

Role of anti-phase boundaries in the formation of magnetic domains in magnetite thin films

Anti-phase boundaries (APBs) are structural defects which have been shown to be responsible for the anomalous magnetic behavior observed in different nanostructures. Understanding their properties is crucial in order to use them to tune the properties of magnetic materials by growing APBs in a controlled way since their density strongly depends on the synthesis method. In this work we investigate their influence on magnetite (Fe3O4) thin films by considering an atomistic spin model, focussing our study on the role that the exchange interactions play across the APB interface. We conclude that the main atypical features reported experimentally in this material are well described by the model we propose here, confirming the new exchange interactions created in the APB as the responsible for this deviation from bulk properties.

Magnetite thin films grown on different flexible polymer substrates at room temperature: Role of antiphase boundaries in electrical and magnetic properties

Currently, there is an enormous need for flexible electronic devices given their astonishing competencies. In this view, we investigated the structural, electrical, and magnetic characterstics of magnetite (Fe3O4) thin films with a thickness of 100 nm prepared using a reactive RF sputtering technique at 300 K on polycarbonate (PC), polymethyl methacrylate (PMMA), and polythene terephthalate (PET) flexible substrates. The structural properties showed that the films grown on PC, PMMA, and PET substrates exhibited the pure form of Fe3O4 nanostructures by flowing oxygen with a flow rate of 3.5 sccm. The Verwey transition temperatures (Tv) of ∼123 K, ∼124 K, and ∼126 K; saturation magnetization (Ms) values of ∼220 emu/cm3, ∼235 emu/cm3, and ∼261 emu/cm3; and magnetoresistance (MR) values of −7.1%, −7.3%, and −7.8% under the H∥Film plane below 60 kOe at 300 K for 100-nm-thick Fe3O4 film on PC, PMMA, and PET substrates respectively were observed. These remarkable results were interpreted and the effect of antiferromagnetically (AFM) coupled antiphase boundaries (APBs) was explained, which suggested that Fe3O4/PET heterostructure can be a most promising component for flexible spintronics.

Fabrication of three-dimensional epitaxial (Fe,Zn)3O4 nanowall wire structures and their transport properties

We have established a unique technique to fabricate three-dimensional (3D) well-defined transition-metal oxide epitaxial nanostructures. Fabrication of epitaxial spinel ferrite Fe2.2Zn0.8O4 (FZO) nanowall wires with a tunable width down to 20 nm was achieved. Cross-sectional transmission electron microscopy revealed the existence of an epitaxially matched lateral interface between the FZO nanowall wire and the side surface of 3D-MgO substrate. Magnetoresistance measurements showed ferromagnetic properties of the FZO nanowall wire at 300 K. The role of antiphase boundaries on the functionalities of the FZO nanoconfined wire is discussed.

Revealing magnetic domain structure in functional Fe2.5Zn0.5O4 wires by transmission electron microscopy

The magnetic and crystallographic microstructures in Fe2.5Zn0.5O4 (FZO) wires fabricated using nano-imprint lithography, pulsed laser deposition and a molybdenum lift-off mask technique were studied by transmission electron microscopy (TEM). A process using a focused ion beam completely separated the FZO wires from the insulating MgO substrate, and accordingly allowed in-depth TEM studies of the domain structures. Observations using energy-filtered TEM demonstrated good crystallinity of the FZO wires. Both Lorentz microscopy and electron holography studies revealed unexpectedly small magnetic domains (∼100nm or smaller) due to a significant interaction with antiphase boundaries. The role of antiphase boundaries on the functionalities observed in the constrained wires (e.g., nonlinear I–V characteristics and large magnetoresistance) is discussed on the basis of these microscopic observations.

The role of antiphase boundaries in the kinetic process of the L1 2 → D0 22 structural change of an Ni 3Al 0.45V 0.50 alloy

The influence of antiphase boundaries (APBs) on the kinetic process of the L1 2 → D0 22 structural change in an Ni 3Al 0.45V 0.50 alloy has been investigated by transmission electron microscopy. The structural change includes two kinetic factors, i.e., the periodic introduction of antiphase-shifted planes (APSPs) in the L1 2 structure and V diffusion in the L1 2 matrix. Our results revealed that APB migration was accompanied by V diffusion as if to sweep the V atoms out of the antiphase domains (APDs). It was also found that the APBs served as the nucleation sites of the D0 22 regions, because the combination of the migrated APBs produced the APSPs in the L1 2 structure. On this basis, it is proposed that the APBs bring together the two kinetic factors in the process of the L1 2 → D0 22 structural change, the physical origin of which is the variation in the charge density distribution of the APDs due to APB migration.

Special features of the order-disorder phase transformation and the role of associated antiphase boundaries

Experimental investigations of the states of long-range order in alloys with the L12, L12(M), L12(MM), and D1a superlattices are discussed. The results obtained enable basic mechanisms involved in the thermal order-disorder transformation to be found and demonstrate an important role of antiphase boundaries in this transition.

The role of antiphase boundaries during ion sputtering and solid phase epitaxy of Si(0 0 1)

The Si(001) surface morphology during ion sputtering at elevated temperatures and solid phase epitaxy (SPE) following ion sputtering at room temperature has been investigated using scanning tunneling microscopy. Two types of antiphase boundaries form on Si(001) surfaces during ion sputtering and SPE. One type of antiphase boundary, the AP2 antiphase boundary, contributes to the surface roughening. AP2 antiphase boundaries are stable up to 700 °C, and ion sputtering and SPE performed at 700 °C result in atomically flat Si(001) surfaces.

Phase stability and electronic structure of theHfAl3compound

First-principles total-energy calculations have addressed the problems of (i) bonding, cohesion, and phase stability and (ii) the role of antiphase boundaries in determining the structural and electronic properties of the ${\mathrm{HfAl}}_{3}$ compound. In this compound, the tetragonal ${D0}_{23}$ structure is stabilized relative to cubic ${L1}_{2}$ by a tetragonal distortion and atomic relaxations. Location of the Fermi level in a pseudogap in the density-of-states distribution rationalizes the calculated structural stabilities. The energetic results are also discussed in the framework of the axial-next-nearest-neighbor Ising model.

Thermodynamic study of the order-disorder transformation for theDO22structure ofα−ln2Te3−I

The thermodynamic stability of the $\ensuremath{\alpha}\ensuremath{-}{\mathrm{ln}}_{2}{\mathrm{Te}}_{3}\ensuremath{-}\mathrm{I}$ system is studied assuming a neostructural transformation of the type ${A}_{1}\ensuremath{\rightarrow}D{O}_{22}$. The appropriate thermodynamic functions for an order-disorder transformation are developed and the question of branching of the long-range parameters is examined in relation to the consequences for the different paths followed by the transformation. The transformation is first order and in passing through the state of partial ordering a clustering is expected in the transition range. This explains the diffuse intensity distributions of electrons, observed previously. Finally, the role of antiphase boundaries in the final arrangement is discussed.