Enhanced Magnetic Component in Synthetic Goethite (α‐FeOOH) and its Relation with Morphological and Structural Characteristics

Abstract

Goethite (α‐FeOOH) is by definition an antiferromagnetic (AFM) material. In the present work an investigation of the magnetic properties of goethite is performed, studying the magnetic component of this material in different samples and relating these properties with its structural and morphological characteristics. Samples are synthetized in two distinct ways in order to generate solids with different degrees of structural defects and imperfections. Electron spin resonance (ESR) data show that the sample synthesized in a faster procedure, most susceptible to defects and imperfections (GC sample), shows an area under the ESR line ≈20 times higher than the sample set for a lower incidence of defects (GD sample). Experiments with heat‐treated samples at 150 °C show a reduction in the number of spins which contributed to ESR signal for the GC sample. Considering data of thermogravimetry (TGA), X‐ray diffraction (XRD), and Mössbauer spectroscopy, the differences observed in ESR analysis are attributed to a magnetic mismatch in the AFM structure caused by the incidence of local defects, more common in GC sample. Results of heat‐treated samples are associated to an increase in the exchange interaction between grains, which reduces the number of mismatched spins and favors the AFM arrangement.

Synthesis and Characterization of Nano Fe and Mn (hydr)oxides to Be Used as Natural Sorbents and Micronutrient Fertilizers

“…For 2L-Fh, the particle size obtained was less than the typical size of 2-lines ferrihydrite particles (2-5 nm) [39]. For goethite, the crystallite sizes resulted from the principal crystallographic planes, which were in line with the results reported by Valezi et al [42]. With respect to the AMO, the particle size was calculated considering the three peaks that denote crystalline forms, since these particles would have been the largest in the material structure.…”

“…Four NMOs (2L-Fh, goethite, AMO and FMBO) were synthetized and properly characterized. FTIR [4,31], XRD [39,42] and Mössbauer spectroscopy [2,53,54] confirmed that 2L-Fh and goethite were well synthesized, with adequate particle size [39,42], PZC [6,19,20,[23][24][25]39] and specific surface area [9,46]. Conversely, the AMO XRD pattern (Figure 2c) confirmed that an amorphous Mn oxide was obtained, and it was undergoing a crystallinity process, as a mixture of manganese oxides [33,40].…”

Ferritin and Free Radicals Species in Seeds by Electron Paramagnetic Resonance

“…The wide resonance line (g ≈ 2.1) shows parameters (Table 1) similar to iron oxides, as goethite (Valezi et al, 2016(Valezi et al, , 2019 and ferrihydrite (Siqueira et al, 2011). The resonance in the center of the six field marker lines (g varying between 2.011 and 2.013), which can be found in some seed's spectra, is identified as a free radical signal.…”

New insights into pertinent Fe-complexes for the synthesis of iron via the instant polyol process

“…29 Fe-based oxides, hydroxides, and complexes were not reduced to iron, whereas iron glycolate and iron alkoxide were utilized to synthesize Fe-oxides in polyols. [30][31][32] Therefore, the direct reduction of Fe in ethylene glycol was presumed to be due to lack of evidence of a reducible intermediate complex within the reaction duration of a few seconds.…”