We perform a combined experimental and theoretical study of a magnetic-field (B)-induced evolution of magnetic and ferroelectric properties in an antiferromagnetic material Pb(TiO)Cu4(PO4)4, whose structure is characterized by a staggered array of Cu4O12 magnetic units with convex geometry known as square cupola. Our experiments show a B-induced phase transition from a previously reported low-B linear magnetoelectric phase to a high-B magnetoelectric phase, which accompanies a 90 flop of electric polarization and gigantic magnetodielectric effect. Moreover, we observe a B-induced sign reversal of ferroelectric polarization in the high-B phase. Our model and first-principles calculations reveal that the observed complex magnetoelectric behavior is well explained in terms of a B-dependent electric polarization generated in each Cu4O12 unit by the so-called exchange-striction mechanism. The present study demonstrates that the materials design based on the magnetic structural unit with convex geometry deserves to be explored for developing strong magnetoelectric couplings.
ASJC Scopus subject areas
- Materials Science(all)
- Physics and Astronomy (miscellaneous)