Characteristic Size Effects on the Crystallographic Structure and Magnetic Properties of RMnO₃ (R = Eu, Gd, Tb, Dy) Nanoparticles

Abstract

We synthesized lanthanoid manganese oxide RMnO 3 (R = Eu, Gd, Tb, and Dy) nanoparticles with particle sizes ranging from approximately 6.5 to 23 nm and investigated both their crystal structure and magnetic properties. The RMnO 3 nanoparticles showed a strong correlation between crystal structure and magnetic properties, and particle size effects on these properties vary owing to the different atomic radii of the lanthanoid ions. The magnetic properties of all of the nanoparticles exhibited significant changes as the lattice constants changed at characteristic sizes that depend on the lanthanoid ionic radius; however, the characteristic size for magnetic properties corresponded to the magnitude of the orthorhombic distortion b/a = 1.10, regardless of the lanthanoid ionic radius. With decreasing particle size, EuMnO 3 , GdMnO 3 , and TbMnO 3 nanoparticles induced tensile strain of MnO 6 octahedra, whereas compressive strain occurred in DyMnO 3 nanoparticles. The deformation of MnO 6 octahedra changed the magnetic interactions, resulting in changes in the magnetic properties. As the particle size decreased, for R = Eu, Gd, and Tb, the magnetic properties, such as transition temperature, coercive field, and blocking temperature, decreased; conversely, these values increased in DyMnO 3 . The distortion of the unit cell induced changes in the magnetic ordering state due to decreasing particle size.

Size Effects of Magneto-Structural Correlation in Mn3O4 Nanoparticles

“…Nanoparticles of strongly correlated materials, particularly manganese oxides, such as RMnO 3 (R = rare earth) and Mn 3 O 4 , are expected to exhibit characteristic size effects on the crystal structure and magnetic properties owing to the strong coupling between the spin, orbital, and lattice. Our previous investigations of rare earth manganese oxide RMnO 3 − and DyMn 2 O 5 have found that the characteristic size dependences of the magnetic properties and crystallographic structures are related to the strong correlation between the crystal structure and the magnetic properties. Moreover, nanoparticles of magnetically frustrated materials are expected to exhibit characteristic size effects.…”

“…Mesoporous silica MCM-41 and SBA-15, which have one-dimensional pores, are a popular mesoporous material for synthesizing magnetic nanoparticles . In our previous study, RMnO 3 (R = La, Eu, Gd, Tb, and Dy), DyMn 2 O 5 , and NiO nanoparticles embedded in SBA-15 were successfully synthesized and their crystal structures and magnetic properties were investigated. − , A mesoporous sulfonated styrene-divinylbenzene copolymer template also was used to produce stable and size-controllable Fe 3 O 4 nanoparticles . In this case, the size control of Fe 3 O 4 nanoparticle was achieved through the change of the ferrous ion concentration incorporated in the polymeric template.…”

Novel Geometric Ferroelectric EuInO3 Single Crystals with Topological Vortex Domains

“…EuInO 3 is isostructural with GdInO 3 , belonging to the hexagonal structure. , However, the ferroelectricity of EuInO 3 is still ambiguous due to the absence of EuInO 3 single crystals. Only a few studies have reported EuInO 3 polycrystals. ,,− Obtaining large single crystals is very important for a detailed investigation by many probes. In order to explore the relationship between the structure and physical properties of EuInO 3 , the EuInO 3 single crystal has been grown by the laser floating zone method in this study.…”

Systematically Designed Surface and Morphology of Magnetite Nanoparticles Using Monocarboxylic Acid with Various Chain Lengths under Hydrothermal Condition

“…Magnetite nanoparticles (Fe 3 O 4 NPs) have attracted attention for various biomedical fields due to their strong magnetic properties and excellent biocompatibility. Recent studies have shown the advantages of Fe 3 O 4 NPs in many biomedical applications such as localized drug delivery, − magnetic resonance imaging (MRI), − and hyperthermia. − However, the high surface energy of NPs typically induces aggregation, which causes difficulties in controlling the size and shape of NPs, significantly affecting the magnetic property. − Additionally, the magnetite is easily oxidized to other thermodynamically stable structures [e.g., maghemite (γ-Fe 2 O 3 ) or hematite (α-Fe 2 O 3 )] in the atmosphere, which leads to the reduction of magnetic saturation . Surface modification in the synthetic field can reduce the surface energy of NPs and enhance the steric hindrance between NPs, thus preventing the aggregation.…”