Abstract
Observation of ferroelectricity among non-d0 systems, which was believed for a long time an unrealistic concept, led to various proposals for the mechanisms to explain the same (i.e. magnetically induced ferroelectricity) during last decade. Here, we provide support for ferroelectricity of a displacive-type possibly involving magnetic ions due to short-range magnetic correlations within a spin-chain, through the demonstration of magnetoelectric coupling in a Haldane spin-chain compound Er2BaNiO5 well above its Néel temperature of (TN = ) 32 K. There is a distinct evidence for electric polarization setting in near 60 K around which there is an evidence for short-range magnetic correlations from other experimental methods. Raman studies also establish a softening of phonon modes in the same temperature (T) range and T-dependent x-ray diffraction (XRD) patterns also reveal lattice parameters anomalies. Density-functional theory based calculations establish a displacive component (similar to d0-ness) as the root-cause of ferroelectricity from (magnetic) NiO6 chain, thereby offering a new route to search for similar materials near room temperature to enable applications.
Highlights
Observation of ferroelectricity among non-d0 systems, which was believed for a long time an unrealistic concept, led to various proposals for the mechanisms to explain the same during last decade
Raman studies establish a softening of phonon modes in the same temperature (T) range and T-dependent x-ray diffraction (XRD) patterns reveal lattice parameters anomalies
The field of magnetoelectric (ME) coupling and multiferroicity involving two correlated phenomena, namely, ferroelectricity and magnetic ordering, bearing relevance to applications, has expanded recently. This kind of multiferroicity has been considered rare in transition-metal systems, as magnetism involves partially filled d orbital and ferroelectricity requires empty d orbital
Summary
Observation of ferroelectricity among non-d0 systems, which was believed for a long time an unrealistic concept, led to various proposals for the mechanisms to explain the same (i.e. magnetically induced ferroelectricity) during last decade. We provide support for ferroelectricity of a displacive-type possibly involving magnetic ions due to short-range magnetic correlations within a spin-chain, through the demonstration of magnetoelectric coupling in a Haldane spin-chain compound Er2BaNiO5 well above its Neel temperature of (TN5) 32 K. The compound under discussion is a Haldane spin-chain compound, Er2BaNiO5, crystallizing in an orthorhombic structure (Immm) We show that this family, R2BaNiO5 (R 5 Rare-earth), is characterized by a strong ME coupling and potentially prone for multiferroicity due to a displacive-type mechanism. In contrast to other R members, in the Er case, the directions of Er and Ni moments point along a-axis at all temperatures below TN13, thereby suiting to the motivation of this work
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