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

TL;DR

This study investigates the magnetic properties of Al$_x$Fe$_{2-x}$GeO$_5$ with andalusite structure, revealing weak ferromagnetism and spin-glass behavior depending on Al content, and discusses the underlying magnetic interactions and site occupancy effects.

Contribution

It provides new insights into how Al substitution affects the magnetic phases and site occupancy in Al$_x$Fe$_{2-x}$GeO$_5$ with andalusite structure.

Findings

Weak ferromagnetic-like state for x<0.3

Spin-glass state for x>0.3

Fe site occupancy influences magnetic behavior

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.