Correlation between ferroic orders of SrFe3O(PO4)3

Geometrically frustrated kagome materials exhibit a variety of exotic states of matter, ranging from quantum spin liquids to multiferroics. In this work, we focus on compounds that display the coexistence of magnetic and ferroelectric orders—known as magnetoelectric multiferroics. The coupling between these orders is of significant technological relevance, particularly for applications such as magnetoelectric random-access memory (MERAM), yet its microscopic origin remains incompletely understood.

SrFe₃O(PO₄)₃, which crystallizes in a quasi-two-dimensional lattice of Fe³⁺ ions with spin 𝑆 = 5/2 , provides an intriguing platform for studying such coupling phenomena. Bulk magnetic characterization and neutron powder diffraction measurements on polycrystalline SrFe₃O(PO₄)₃ reveal two successive magnetic transitions: a weak ferromagnetic-type ordering at 𝑇𝐶1≈25 K, followed by another transition at T2 = 8 K. The neutron diffraction data indicate that SrFe₃O(PO₄)₃ adopts a ferromagnetic structure below T1 and overall antiferromagnetic arrangement below T2. We discuss the origin of these non-collinear magnetic ground states and present the corresponding magnetic phase diagram as a function of applied magnetic field.