Observation of magnetic-field-induced ferroelectricity in a compound CaFe3O(PO4)3

Abstract

Geometrically frustrated kagome materials reveal many novel states of matter ranging from quantum spin liquids to multiferroics. Herein, we study the compound CaFe3O(PO4)3, which has a quasi-two-dimensional lattice of Fe3+ ions with spin S = 5/2. Electrical and magnetic properties have been investigated on polycrystalline specimens of CaFe3O(PO4)3 using magnetization, pyroelectric, and magnetoelectric current measurements. The system undergoes a weak ferromagnetic-type ordering at TC1 ∼ 19.5 K, followed by another transition at TC2 ∼ 9 K. While no ferroelectric polarization (P) is observed at a zero magnetic field (H), the applied H induces P below TC2. At the temperature of 2.5 K, P starts to increase above H of 1 T, shows a maximum value at 3.15 T, and then decreases at higher H regions. The observed results suggest that CaFe3O(PO4)3 should be a magnetic-field-induced ferroelectric compound with frustrated magnetic couplings.