Natural ferroelectric order near ambient temperature in the orthoferrite HoFeO3

Abstract

Current scenario in multiferroics demands a breakthrough discovery of promising materials after BiFeO3. Recently, the controversial discovery of room temperature ferroelectricity (FE) in SmFeO3 [PRL 107, 117201 (2011); 113, 217203 (2014)] inspires the investigation of HoFeO3. Here, we report a natural ferroelectric order below 210 K (TF E ) along c-axis with reasonably large polarization and low-field strong magnetoelectric coupling. Synchrotron and neutron diffraction results confirm that a shift of O atoms along c-axis of polar P b ′ n ′ 21 structure causes FE in HoFeO3. The exchange striction mechanism is suggested to elucidate the ferroelectric order. The results create a renewed attention for searching promising candidates with a natural ferroelectric order and higher TF E in the rest of the RFeO3 series.

An antisite defect mechanism for room temperature ferroelectricity in orthoferrites

“…3a). The polarization observed here is orders of magnitude stronger than the values reported previously in bulk RFeO3, R=Gd 20 , Dy 21 , Ho 22 and Sm 23 , and comparable with a measurement reported by Shang et al in thin film YFO 28 .…”

“…The mechanism is attributed to the exchange-striction effect of R 4f and Fe 3d spins, and hence the ferroelectricity only occurs below the R 4f spin ordering temperature of a few Kelvin. In HoFeO3 22 and SmFeO3 23 , ferroelectricity is reported to be present near or even above room temperature, but contradictory conclusions from theoretical 24 and experimental 25,26 work have obscured the mechanism, particularly in the case of room temperature ferroelectricity reported in YFeO3 (YFO) 27,28,29 . YFO adopts a space group Pbnm with lattice parameters of ao=5.282 Å, bo=5.595 Å, co=7.605 Å (the subscript o denotes the orthorhombic notation).…”

Structural correlation to ferroelectric order, non-Griffiths like phase and magnetocaloric effect in YbCrO4

“…The structural study attempts to extract knowledge from the crystallography and understanding origins of the different multifunctional properties of the system. The structural correlation to the electrical and magnetic properties has been recently found crucial in few systems, which provides rich consequences in solid state such as colossal magnetoresistance [1], giant magnetocaloric effect [2], Griffiths phase singularities [3], spontaneous ferroelectric order [4,5], multiferroic order [6]. In the current observation we report important structural correlations to the various unexplored multifunctional properties of YbCrO 4 .…”

Pr-Doping Effect on Spin Switching in Nd0.8Pr0.2FeO3 Single Crystal

“…Type-I SSW means that when the temperature of the system reaches a specific point, the total magnetization of R FeO 3 will suddenly change the sign while its magnitude remains unchanged, indicating that both R 3+ and Fe 3+ magnetic moments simultaneously reverse at the temperature point. This behavior can be observed in PrFeO 3 , NdFeO 3 , , SmFeO 3 , − HoFeO 3 , − ErFeO 3 , ,− and TmFeO 3 . , Moreover, when type-II SSW occurs, only R 3+ moments will flip, while Fe 3+ moments remain unchanged, making the antiparallel (parallel) coupling of Fe 3+ and R 3+ moments parallel (antiparallel), showing a sudden jump (or drop) in magnetization macroscopically. Such effect has been reported in PrFeO 3 and DyFeO 3 . , Besides pure phase compounds, the effects of rare earth doping R FeO 3 show even more complex magnetic behavior because of varying interactions between rare earth and iron ions moments, such as multiple spin reorientation transitions, spin switching effects and so on. − …”