Weak trimer distortion and planar spin configuration in hexagonal Lu0.6In0.4FeO3.

Improper ferroelectricity and canted ferromagnetism in antiferromagnetically ordered hexagonal ferrites with A₂-type spin configuration have been intensely studied due to their potential for room-temperature multiferroicity with strong magnetoelectric couplings. However, the subtle interplay between the magnetic structure and trimer structural distortion, which is a critical ingredient for ferroelectricity, has not been clearly verified in experiments due to the lack of control over trimer distortion. In this study, we report on Lu_0.6In_0.4FeO₃, which exhibits weaker trimer distortion primarily related to the smaller tilting of the FeO₅ bipyramids. The reduced vertical displacement of the equatorial oxygen of FeO₅ located at the center of the trimer lowers the magnitude of the in-plane Dzyaloshinskii–Moriya vector component, resulting in the absence of canted ferromagnetism with the planar A₁-type spin configuration, rather than the canted A₂-type observed in other hexagonal ferrites. Our findings demonstrate that the degree of trimer distortion plays an important role in determining the spin configuration in related hexagonal systems. [ABSTRACT FROM AUTHOR]