Frustrated Magnetism in FeGe$_3$O$_4$ with a Chiral Trillium Network

TL;DR

This study introduces FeGe$_3$O$_4$, a new frustrated magnet with a trillium lattice, showing complex magnetic behavior and strong frustration effects, making it a promising candidate for exploring exotic quantum phenomena.

Contribution

It reports the synthesis, structural characterization, and magnetic properties of FeGe$_3$O$_4$, a novel compound with a frustrated trillium lattice, expanding the understanding of geometrically frustrated magnetic materials.

Findings

FeGe$_3$O$_4$ has a noncentrosymmetric cubic structure with a double-trillium lattice.

Magnetization shows no saturation up to 70 kOe, indicating complex magnetic interactions.

Strong magnetic frustration is evidenced by partial entropy recovery and absence of long-range order down to 0.06 K.

Abstract

The discovery of new magnetic ground states in geometrically frustrated lattices remains a central challenge in materials science. Here, we report the synthesis, structural characterization, and frustrated magnetic properties of FeGe$_3$O$_4$, a newly identified compound that crystallizes in the noncentrosymmetric cubic space group $P2_13$. In this structure, Fe atoms form an intricate double-trillium lattice with nearest-neighbor Fe--Fe distances of $\sim$4.2~\AA{}, while Ge$^{2+}$ ions mediate magnetic interactions through Fe-Ge-Fe pathways. Field-dependent magnetization at 2~K shows a pronounced nonlinearity, reaching a maximum moment of 2.55(3)~$\mu_\mathrm{B}$/Fe$^{2+}$ at 70~kOe without evidence of saturation. Magnetic susceptibility, heat capacity, and neutron scattering collectively reveal the onset of short-range magnetic interactions near 5~K, with no long-range ordering detected down to 0.06~K. Specific heat measurements demonstrate strong frustration: only $\sim$34\% of the expected magnetic entropy is recovered at 2.4~K. Taken together, these results establish FeGe$_3$O$_4$ as a rare example of a geometrically frustrated trillium-lattice magnet, offering a promising platform for exploring exotic quantum magnetic phenomena.