Canted antiferromagnetic and optical properties of nanostructures of Mn ₂ O ₃ prepared by hydrothermal synthesis

Abstract

We have reported new magnetic and optical properties of Mn 2 O 3 nanostructures. The nanostructures have been synthesized by the hydrothermal method combined with the adjustment of pH values in the reaction system. The particular characteristics of the nanostructures have been analyzed by employing X-Ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), Raman spectroscopy (RS), UV-visible spectroscopy, and the vibrating sample magnetometer (VSM). Structural investigation manifests that the synthesized Mn 2 O 3 nanostructures are orthorhombic crystal. Magnetic investigation indicates that the Mn 2 O 3 nanostructures are antiferromagnetic and the antiferromagnetic transition temperature is at T N = 83 K. Furthermore, the Mn 2 O 3 nanostructures possess canted antiferromagnetic order below the Neel temperature due to spin frustration, resulting in hysteresis with large coercivity (1580 Oe) and remnant magnetization (1.52 emu/g). The UV-visible spectrophotometry was used to determine the transmittance behaviour of Mn 2 O 3 nanostructures. A direct optical band gap of 1.2 eV was acquired by using the Davis-Mott model. The UV-visible spectrum indicates that the absorption is prominent in the visible region, and transparency is more than 80% in the UV region.

Magnetic Properties of Reduced and Reoxidized Mn–Na2WO4/SiO2: A Catalyst for Oxidative Coupling of Methane (OCM)

“…on the silica support used here, were shown to exhibit magnetic ordering. 17,19,34,[42][43][44][45] Apparently, the formation of long-range ordered magnetic phases reports on a massive restructuring of the catalyst depending on its oxidation state affecting a large part of the Mn-Na 2 WO 4 layer. However, they exhibit sufficiently short distances between the magnetic Mn centers resulting in significant spin-spin interaction, which explains the observed cw EPR results.…”

Evaluating transition metal oxides within DFT-SCAN and SCAN+U frameworks for solar thermochemical applications

“…34 For example, DFT-SCAN predicts metallic behavior for Ce2O3, Mn2O3, MnO2, FeO, and Fe3O4, in contrast to their observed semiconducting behavior at low temperatures. 73,[96][97][98][99]101 The deviations in DFT-SCAN band gaps are particularly severe for Ce2O3, Mn2O3, and FeO, which exhibit reasonable band gaps experimentally (> 1 eV). We do not find semiconducting behavior for MnO2 with SCAN (DOS plotted in Figure S2 of the SI), unlike a previous report 35 where the authors used a fairly coarse k-point grid (at intervals of 0.25 Å -1 ).…”

Manganese oxide phases and morphologies: A study on calcination temperature and atmospheric dependence

“…Several nanoscale manganese oxide compounds can be prepared via calcination processes from suitable precursors [7,[18][19][20]. Whereas many synthetic protocols yield manganese oxide species at the nanometer scale [21], for example, precipitation or the solvothermal route, these methods require long reaction times in the range of hours (up to 24 h) and subsequent drying processes of up to 2 days [22][23][24][25][26][27]. The synthesis via oxidation of manganese metal nanoparticles by gas condensation must be followed by annealing in O 2 -containing atmospheres to obtain different manganese oxide species [28].…”