Room-Temperature Antiferroelectricity in Multiferroic Hexagonal Rare-Earth Ferrites

Abstract

The antiferroelectric (AFE) phase, in which nonpolar and polar states are switchable by an electric field, is a recent discovery in promising multiferroics of hexagonal rareearth manganites (ferrites), h-RMn(Fe)O 3 . However, this phase has so far only been observed at 60−160 K, which restricts key investigations into the microstructures and magnetoelectric behaviors. Herein, we report the successful expansion of the AFE temperature range (10−300 K) by preparing h-DyFeO 3 films through epitaxial stabilization. Room-temperature scanning transmission electron microscopy reveals that the AFE phase originates from a nanomosaic structure comprising AFE P3̅ c1 and ferroelectric P6 3 cm domains with small domain sizes of 1− 10 nm. The nanomosaic structure is stabilized by a low c/a ratio derived from the large ionic radius of Dy 3+ . Furthermore, weak ferromagnetism and magnetocapacitance behaviors are observed. Below 10 K, the film exhibits an M-shaped magnetocapacitance versus magnetic field curve, indicating unusual magnetoelectric coupling in the AFE phase.

Antiferroelectric-to-ferroelectric phase transition in hexagonal rare-earth iron oxides

“…21 Because this tilting is related to the lattice parameters, the FE properties can be modulated by changing the c/a ratio. 24 For example, h-RFeO 3 exhibits FE behavior when c/a exceeds 1.93, [25][26][27][28][29] while it shows AFE behavior when c/a = 1.89. 24 However, the boundary between the AFE and FE phases remains unknown, resulting in the absence of a AFE-FE phase transition in one crystal of h-RFeO 3 .…”

DyFe2O4: A new trigonal rare-earth ferrite grown by molecular-beam epitaxy

“…The stable polymorph of DyFeO 3 is an orthorhombic perovskite structure. Nevertheless, h-DyFeO 3 has been epitaxially stabilized before 42,43 and appears to be a strong competitor in this system as films were observed to preferentially form in a mixture of DyFe 2 O 4 and h-DyFeO 3 if there was any excess dysprosium or higher levels of oxygen. Rather than considering the metastability vs the convex hull of bulk stable phases, i.e.,…”

“…In the similar system of LuFe 2 O 4 , although phase-pure LuFe 2 O 4 was able to be deposited by MBE, 11 other groups could only find growth regimes where a mixture of LuFe 2 O 4 and h-LuFeO 3 would form. 44 The a lattice parameter of h-DyFeO 3 is effectively smaller 42 The lattice parameters of the DyFe 2 O 4 films were calculated from x-ray diffraction and yield a = 3.540 ± 0.007 Å and c = 24.90 ± 0.06 Å. The c lattice parameter was calculated using Nelson-Riley plots 45 of the first four 003l film peaks and then averaged over five films.…”

Hexagonal Ferrites, Synthesis, Properties and Their Applications

“…With the discovery of hexagonal ferrites in 1950's, there has been a continuous completion in exploring more exotic properties of hexa-ferrites. Most of the research works on hexa-ferrites are concentrated on their complex structure, structure modified properties and applications of theses ferrites [3][4][5][6]. Growing interest in the field of hexagonal ferrites can be analysed viewing the number of papers published on hexagonal ferrites during 2010-2020.…”