Magnetism of Al\(_x\)Fe\(_{2-x}\)GeO\(_5\) with Andalusite Structure

Abstract

The magnetism of Al\(_x\)Fe\(_{2-x}\)GeO\(_5\) from \(x\) = 0.09 to \(x\) = 0.91 with andalusite structure was examined. The magnetic properties of Al\(_x\)Fe\(_{2-x}\)GeO\(_5\) at low temperatures were found to be weak ferromagnetic-like state for \(x\) \(<\) 0.3 and spin-glass state for \(x\) \(>\) 0.3. The small spontaneous magnetization that appears in the weak ferromagnetic-like phase would be due to the presence of Dzyaloshinsky-Moriya interaction or to the difference in the magnitude of the magnetic moment of Fe\(^{3+}\) in the octahedral and trigonal bipyramidal sites. The appearance of the spin-glass phase indicates that the dilution of Fe ions by Al ions in Al\(_x\)Fe\(_{2-x}\)GeO\(_5\) causes the competition between ferromagnetic and antiferromagnetic interactions. The \(x\) dependence of the site occupancy of Fe ions suggests that Fe\(_2\)GeO\(_5\) with andalusite structure cannot be synthesized.