Frustrated Magnetism in FeGe ₃ O ₄ with a Chiral Trillium Network

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 FeGe₃O₄, a newly identified compound that crystallizes in the noncentrosymmetric cubic space group P2₁3. In this structure, Fe atoms form an intricate double-trillium lattice with nearest-neighbor Fe-Fe distances of ∼4.2 Å, while Ge²⁺ 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) μB/Fe²⁺ 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 ∼34% of the expected magnetic entropy is recovered at 2.4 K. Taken together, these results establish FeGe₃O₄ as a rare example of a geometrically frustrated trillium lattice magnet, offering a promising platform for exploring exotic quantum magnetic phenomena.