Interplay of surface conditions, particle size, stoichiometry, cell parameters, and magnetism in synthetic hematite-like materials

  title={Interplay of surface conditions, particle size, stoichiometry, cell parameters, and magnetism in synthetic hematite-like materials},
  author={M.-Z. Dang and Denis Rancourt and John E. Dutrizac and Gilles Lamarche and Robert Provencher},
  journal={Hyperfine Interactions},
We have studied several synthetic hematite-like materials, produced via different reactions using various hydrothermal conditions and various temperatures of annealing in air, by bulk elemental analysis, weight loss measurements, scanning electron microscopy, powder X-ray diffraction, Mössbauer spectroscopy, and SQUID magnetometry. We conclude that hematite-like materials cannot be related to pure stoichiometric hematite via a single stoichiometric or physical parameter and that at least two… 
Morin transition in hematite: Size dependence and thermal hysteresis
[1] Hematite is a frequently used mineral in paleomagnetic and environmental magnetic studies. Just below room temperature, it undergoes a magnetic phase transition, the Morin transition, whose
Annealing control of hydrothermally grown hematite nanorods: Implication of structural changes and Cl concentration on weak ferromagnetism
Abstract In-situ X-ray diffraction coupled with thermogravimetry and differential scanning calorimetry were used to elucidate the crystal phase transition from akaganeite to hematite nanorods. The
A refined monoclinic structure for a variety of “hydrohematite”
Abstract In ferruginous soils, nano- to microscale hematite (α-Fe2O3) plays a central role in redox processes and contaminant cycling. Hematite is known to incorporate structural OH- and water, and
Size-dependent structural transformations of hematite nanoparticles. 1. Phase transition.
A general model is developed that considers spinel defects and absorbed/adsorbed species as dominant controls on structural changes with particle size in hematite nanoparticles, including solid-state phase transitions, and supports the existence of intermediate phases during dehydration of goethite.
Changes in the structural and magnetic properties of Ni–substituted hematite prepared from metal oxinates
Samples prepared by the novel method based on the thermal decomposition at 700 °C in air of mixed Fe and Ni oxinates were characterized by thermogravimetric analysis, X-ray diffraction, magnetization
Magnetic and structural properties of pure hematite submitted to mechanical milling in air and ethanol
Abstract The mechanochemical treatment of α-Fe2O3 (hematite) powder in air and in ethanol at different times using a planetary ball mill was performed. X-ray diffraction (XRD) using Rietveld analysis
Effects of milling-induced disorder on the lattice parameters and magnetic properties of hematite
Abstract A ball-milling treatment in air for 30 min is enough to reduce anhydrous bulk hematite (α-Fe 2 O 3 ) grains to nanometric sizes. For milling times, t m , of 15, 30 min, 1 and 2 h, the
Magnetic properties of hematite with large coercivity
The magnetic properties of hematite powders produced by a solid state nucleation-and-growth process are studied as a function of temperature T and applied field H. Independently of the temperature,
Field-induced spin–flop transitions of interacting nanosized α-Fe2O3 particles dispersed in a silica glass matrix
Nanoparticles of 10 mol% Fe2O3 doped in silica glass (Fe10) samples prepared by a sol–gel method followed by calcination at various temperatures in the range 700–1000 °C are studied by x-ray,
High-yield synthesis and magnetic property of hematite nanorhombohedras through a facile solution route
Abstract Through a relatively low temperature solution route, hematite (α-Fe 2 O 3 ) nanorhombohedras with average particle size of 35 nm were synthesized in high yield. The final products were


Shape effects on crystallite size distributions in synthetic hematites from X-ray line-profile analysis
Abstract Synthetic acicular hematite shows a nonuniform broadening of the X-ray lines in a wide temperature range. The factors affecting the peak broadening were studied by recording the powder line
Mössbauer effect study of the spin structure in natural hematites
Three natural hematites, α-Fe2O3, from the region of Elba have been investigated by means of 57Fe Mössbauer spectroscopy at variable temperatures between 80 and 400K. The samples were selected on the
Magnetic properties of microcrystalline iron (III) oxides and related materials as reflected in their Mössbauer spectra
Iron (III) oxides are common constituents of geologic materials, they are products and by-products of many industrial processes, they are involved in biological processes, and they are the outcome of
Particle size determination in supported iron oxide (.alpha.-Fe2O3)
The techniques of high-angle x-ray diffraction line profile analysis, transmission electron microscopy, and Moessbauer effect spectroscopy have been applied to the study of ..cap alpha..-Fe/sub
Nonstoichiometric structures during dehydroxylation of goethite
Thermal dehydration of goethite (a-FeOOH) at low temperature leads to complete transformation into a hematite-like phase before less than one half of the stoichiometric water content in goethite is
Mössbauer characterization of very small superparamagnetic particles; application to intra-zeolitic α-Fe2O3 particles
Abstract The Mossbauer spectra of very small α-Fe 2 O 3 particles supported by zeolite-Y were taken at various temperatures above and below the blocking temperature. A new technique for calculating
A Mössbauer study of magnetic relaxation and the Morin transition in amorphous and crystalline iron oxide systems
Abstract In this work magnetic effects are studied by Mossbauer spectroscopy in microcrystalline iron oxides. The samples were prepared from iron nitrate under a variety of conditions using a simple
Mössbauer effect studies of surface ions of ultrafine α‐Fe2O3 particles
Since in ultrafine particles a considerable fraction of the atoms is located near or at the surface the behaviour of these atoms is studied using the Mossbauer technique. The contribution to the
Effect of heat treatment on microstructure evolution of haematite derived from synthetic goethite
Abstract The evolution of the microstructure of α-Fe 2 O 3 derived from synthetic α-FeOOH in a wide temperature range (400–1100 °C) has been systematically investigated using X-ray powder
Mössbauer studies of the morin transition in bulk and microcrystalline α-Fe2O3†
Abstract Mossbauer spectra of bulk and microcrystalline hematite have been analyzed at the Morin transition for both the weak-ferromagnetic (WF) and anti-ferromagnetic (AF) phases simultaneously,