Direct evidence for weak ferromagnetism sustained by Fe2+-O-Fe3+ superexchange coupling in short-range structures of aluminosilicate glasses

We report on the magnetism of amorphous SiO2-Al2O3-CaO-MgO-Fe2O3-K2O-MnO:CA (CA-activated carbon) aluminosilicate glasses prepared by a fusion-quenching method. Fourier transform infrared and Raman spectroscopy show that a Fe2+ lattice modifier in the glass structures induces depolymerization, strongly influencing the magnetic transitions. Room temperature magnetization measurements of the CA-glasses show a different magnetic behavior, such as speromagnetism, asperomagnetism, and weak ferromagnetism. Mo euro ssbauer spectroscopy analyses at room temperature reveal that iron changes valence from Fe3+-> Fe2+ with increasing CA content. This Fe3+-> Fe2+ suggests that asperomagnetism and weak ferromagnetism behavior are triggered by Fe2+-O-Fe3+ superexchange coupling in short-range structures of aluminosilicate glasses. A model for the aluminosilicate glass structures is proposed to explain the different magnetic regimes.

Automated summary

We report the magnetism of amorphous SiO2-Al2O3-CaO-MgO-Fe2O3-K2O-MnO: CA (CA-activated carbon) aluminosilicate glasses prepared by a fusion-quenching method. The presence of Fe2+ lattice modifier in the glass structures induces depolymerization, greatly affecting the magnetic transitions. Room temperature magnetization measurements reveal different magnetic behaviors, including speromagnetism, asperomagnetism, and weak ferromagnetism, in the CA-glasses. Analysis through Mo ssbauer spectroscopy at room temperature suggests that the change in valence from Fe3+-> Fe2+ triggers the asperomagnetism and weak ferromagnetism, due to Fe2+-O-Fe3+ superexchange coupling in short-range structures of the aluminosilicate glasses. A proposed model explains the different magnetic regimes in the aluminosilicate glass structures.