Magnetic structure and multiferroicity of Sc-substituted hexagonal YbFeO$_3$

TL;DR

This study stabilizes the hexagonal structure of YbFeO$_3$ via Sc substitution, revealing complex magnetic ordering and magnetoelectric coupling, advancing the search for high-temperature multiferroics in hexagonal ferrites.

Contribution

It demonstrates stabilization of hexagonal YbFeO$_3$ through partial Sc substitution and elucidates its magnetic and ferroelectric properties, highlighting potential for high-temperature multiferroic applications.

Findings

Yb$_{0.42}$Sc$_{0.58}$FeO$_3$ orders antiferromagnetically below 165 K.

Magnetic moments reorient below 40 K, with Yb moments ordering at 15 K.

Electric polarization can be modulated by magnetic field at low temperatures.

Abstract

Hexagonal rare-earth ferrite RFeO$_3$ family represents a unique class of multiferroics exhibiting weak ferromagnetism, and a strong coupling between magnetism and structural trimerization is predicted. However, the hexagonal structure for RFeO$_3$ remains metastable in conventional condition. We have succeeded in stabilizing the hexagonal structure of polycrystalline YbFeO$_3$ by partial Sc substitution of Yb. Using bulk magnetometry and neutron diffraction, we find that Yb$_{0.42}$Sc$_{0.58}$FeO$_3$ orders into a canted antiferromagnetic state with the Neel temperature $T_N$ ~ 165 K, below which the $Fe^{3+}$ moments form the triangular configuration in the $ab$-plane and their in-plane projections are parallel to the [100] axis, consistent with magnetic space group $P$6$_{3}$$c'm'$. It is determined that the spin-canting is aligned along the $c$-axis, giving rise to the weak ferromagnetism. Furthermore, the $Fe^{3+}$ moments reorient toward a new direction below reorientation temperature $T_R$ ~ 40 K, satisfying magnetic subgroup $P$6$_{3}$, while the $Yb^{3+}$ moments order independently and ferrimagnetically along the $c$-axis at the characteristic temperature $T_{Yb}$ ~ 15 K. Interestingly, reproducible modulation of electric polarization induced by magnetic field at low temperature is achieved, suggesting that the delicate structural distortion associated with two-up/one-down buckling of the Yb/Sc-planes and tilting of the FeO$_5$ bipyramids may mediate the coupling between ferroelectric and magnetic orders under magnetic field. The present work represents a substantial progress to search for high-temperature multiferroics in hexagonal ferrites and related materials.