Single-crystal growth and magnetic, magnetoelectric, and optical properties of ferroaxial-type SrMn${}_2$Ni${}_6$Te${}_3$O${}_{18}$

Abstract

Single crystals of SrMn${}_2$Ni${}_6$Te${}_3$O${}_{18}$, a member of the ferroaxial-type magnetic oxide family $A{B}_2{C}_6$Te${}_3$O${}_{18}$ ($A$ = Pb, Sr; $B$ = Mn, Cd; $C$ = Ni, Co), have been successfully grown, and their structural, magnetic, magnetoelectric, and optical properties have been systematically studied. Imaging of the spatial distribution of electric-field-induced optical rotation reveals that the single crystals preferentially form single ferroaxial (FA) domains. Magnetization and neutron diffraction measurements show that Mn${}^{2+}$ and Ni${}^{2+}$ magnetic moments order antiferromagnetically at $T_{\mathrm{N}}$ = 83 K, forming a $c$-axis collinear bidirector-type antiferromagnetic structure. All independent magnetoelectric tensor components allowed by the magnetic point group 6/$m^{\prime }$ have been detected, and the ${\chi }_{33}$ component exhibits a pronounced temperature-dependent anomaly, including a peak and a sign reversal. Preferential formation of single FA domains and a similar ${\chi }_{33}$ anomaly are also observed in the isostructural compound PbMn${}_2$Ni${}_6$Te${}_3$O${}_{18}$. These findings suggest that the ferroaxial and magnetic characteristics within this structural framework are robust against Sr-Pb replacement.