Magnetic structure and multiferroicity of Sc-substituted hexagonal YbFeO3

Abstract

Hexagonal rare-earth ferrite RFeO3 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 RFeO3 remains metastable in conventional condition. We have succeeded in stabilizing the hexagonal structure of polycrystalline YbFeO3 by partial Sc substitution of Yb. Using bulk magnetometry and neutron diffraction, we find that Yb0.42Sc0.58FeO3 orders into a canted antiferromagnetic state with the Néel temperature TN ~ 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 P63c'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 TR ~ 40 K, satisfying magnetic subgroup P63, while the Yb 3+ moments order independently and ferrimagnetically along the c-axis at the characteristic temperature TYb ~ 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 FeO5 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.

Nonzero Spontaneous Magnetic Moment along the b-Axis and the 2-Fold Spin Reorientation Transition in a Er0.4Gd0.6FeO3 Single Crystal

“…Rare-earth orthoferrites (RFeO 3 ) have a distorted perovskite structure with a space group of Pbnm . − As a functional material family, RFeO 3 attracts great scientific interest and has technological significance for potential applications such as magneto-optical switch, ultrafast optomagnetic recording, precession excitation induced by terahertz pulses, and magnetism-induced ferroelectric multiferroics. − Their abundant magnetic properties mainly originate from 3d-electrons of Fe 3+ and 4f-electrons of R 3+ . , The two magnetic ions (R 3+ and Fe 3+ ) form in three types of magnetic sublattices, including Fe 3+ –Fe 3+ , Fe 3+ –R 3+ , and R 3+ –R 3+ sublattices . The strongest one of those is Fe 3+ –Fe 3+ with G-type antiferromagnetic interaction, which causes the iron ions to orient opposite to all nearest neighbors in three dimensions below the first Neel temperature at 650–700 K. The presence of a Dzyaloshinskii–Moriya interaction − induces an asymmetric electronic exchange, resulting in a spontaneous magnetization in the c -axis of a RFeO 3 single crystal below the Neel temperature.…”