Magnetoferroelectric phase transition induced by latent spin-lattice coupling in the geometrically frustrated magnet

玉造 博夢; 内原 猛*; 満田 節生*; 石井 祐太*; 中尾 裕則*; 竹端 寛治*; 今中 康貴*

Physical Review B, 111(13), p.134403_1 - 134403_9, 2025/04

https://doi.org/10.1103/PhysRevB.111.134403

In multiferroic CuFeAlO, applying uniaxial pressure generates a magnetoferroelectric phase distinct from the well-studied spin-driven ferroelectric phase associated with helical magnetic ordering in this system. Using a four-circle neutron diffractometer, the magnetic structure of the -induced magnetoferroelectric phase is determined as the collinear sinusoidal type, which itself does not break the inversion symmetry in this system. Additionally, synchrotron radiation X-ray diffraction experiments are conducted to investigate how the triangular lattice in CuFeAlO is distorted by applied . Although lattice distortion during the magnetic phase transition in CuFeAlO is mitigated by the substitution of nonmagnetic Al, the application of along the conjugate direction revives the "latent" spin-lattice coupling, causing the triangular lattice to distort during magnetic phase transition. The application of a magnetic filed considerably reduces -induced ferroelectric polarization, but does not affect lattice distortion. These results indicate that -induced ferroelectric polarization is not a consequence of the piezoelectric effect. Instead, the sinusoidal magnetic structure would contribute to the emergence of -induced ferroelectric polarization through spin-lattice coupling.