Room-Temperature Polar Ferromagnet ScFeO₃ Transformed from a High-Pressure Orthorhombic Perovskite Phase

Multiferroic materials have been the subject of intense study, but it remains a great challenge to synthesize those presenting both magnetic and ferroelectric polarizations at room temperature. In this work, we have successfully obtained LiNbO₃-type ScFeO₃, a metastable phase converted from the orthorhombic perovskite formed under 15 GPa at elevated temperatures. A combined structure analysis by synchrotron X-ray and neutron powder diffraction and high-angle annular dark-field scanning transmission electron microscopy imaging reveals that this compound adopts the polar <i>R</i>3<i>c</i> symmetry with a fully ordered arrangement of trivalent Sc and Fe ions, forming highly distorted ScO₆ and FeO₆ octahedra. The calculated spontaneous polarization along the hexagonal <i>c</i>-axis is as large as 100 μC/cm². The magnetic studies show that LiNbO₃-type ScFeO₃ is a weak ferromagnet with <i>T</i>_N = 545 K due to a canted <i>G</i>-type antiferromagnetic ordering of Fe³⁺ spins, representing the first example of LiNbO₃-type oxides with magnetic ordering far above room temperature. A comparison of the present compound and rare-earth orthorhombic perovskites RFeO₃ (R = La–Lu and Y), all of which possess the corner-shared FeO₆ octahedral network, allows us to find a correlation between <i>T</i>_N and the Fe–O–Fe bond angle, indicating that the A-site cation-size-dependent octahedral tilting dominates the magnetic transition through the Fe–O–Fe superexchange interaction. This work provides a general and versatile strategy to create materials in which ferroelectricity and ferromagnetism coexist at high temperatures

Room-Temperature Polar Ferromagnet ScFeO₃ Transformed from a High-Pressure Orthorhombic Perovskite Phase

Multiferroic materials have been the subject of intense study, but it remains a great challenge to synthesize those presenting both magnetic and ferroelectric polarizations at room temperature. In this work, we have successfully obtained LiNbO₃-type ScFeO₃, a metastable phase converted from the orthorhombic perovskite formed under 15 GPa at elevated temperatures. A combined structure analysis by synchrotron X-ray and neutron powder diffraction and high-angle annular dark-field scanning transmission electron microscopy imaging reveals that this compound adopts the polar <i>R</i>3<i>c</i> symmetry with a fully ordered arrangement of trivalent Sc and Fe ions, forming highly distorted ScO₆ and FeO₆ octahedra. The calculated spontaneous polarization along the hexagonal <i>c</i>-axis is as large as 100 μC/cm². The magnetic studies show that LiNbO₃-type ScFeO₃ is a weak ferromagnet with <i>T</i>_N = 545 K due to a canted <i>G</i>-type antiferromagnetic ordering of Fe³⁺ spins, representing the first example of LiNbO₃-type oxides with magnetic ordering far above room temperature. A comparison of the present compound and rare-earth orthorhombic perovskites RFeO₃ (R = La–Lu and Y), all of which possess the corner-shared FeO₆ octahedral network, allows us to find a correlation between <i>T</i>_N and the Fe–O–Fe bond angle, indicating that the A-site cation-size-dependent octahedral tilting dominates the magnetic transition through the Fe–O–Fe superexchange interaction. This work provides a general and versatile strategy to create materials in which ferroelectricity and ferromagnetism coexist at high temperatures