Rare earth size dependence on structural, electronic and magnetic properties of R2NiMnO6 double perovskites

Rare earth Manganite Nickelite double perovskites are prepared by solgel assisted combustion route, where, R varies from La, Pr, Nd, Sm, Gd, Tb, Dy, Y, and Ho. The samples have been systematically investigated using powder xray diffraction, Raman spectroscopy, ultraviolet visible spectroscopy, magne...

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Bibliographic Details
Published in:arXiv.org 2018-08
Main Authors: Nasir, Mohd, Kumar, Sunil, Patra, N, Bhattacharya, D, Jha, S N, Basaula, Dharma R, Bhatt, Subhash, Khan, Mahmud, Shun Wein Liu, Biring, Sajal, Sen, Somaditya
Format: Article
Language:English
Subjects:
Curie temperature
Dependence
Distortion
Dysprosium
Elongation
Gadolinium
Lanthanum
Lattice parameters
Lattice vibration
Magnetic moments
Magnetic properties
Magnetic saturation
Magnetism
Magnetization
Manganese
Metal ions
Neodymium
Nickel
Perovskites
Raman spectra
Raman spectroscopy
Rare earth elements
Spectrum analysis
X ray absorption
X ray powder diffraction
X-ray diffraction
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Summary:Rare earth Manganite Nickelite double perovskites are prepared by solgel assisted combustion route, where, R varies from La, Pr, Nd, Sm, Gd, Tb, Dy, Y, and Ho. The samples have been systematically investigated using powder xray diffraction, Raman spectroscopy, ultraviolet visible spectroscopy, magnetization, and synchrotron based xray absorption spectroscopy measurements. All compounds in the family crystallize in the monoclinic structure and the monoclinic distortion enhances with decreasing trivalent rare earth radii. The magnetic ordering temperature, Tc, decreases from 270 K for La to 80 K for Ho samples as the rare earth radii decrease from 0.116nm for La to 0.102nm in case of Ho. An additional anomaly is observed in samples containing Nd, Sm, Tb, and Dy at lower temperatures, which originates from the 3d to 4f coupling between Mn and Ni and Nd, Sm, Tb and Dy magnetic moments. Further, high saturation magnetization is achieved for all samples indicating that they are atomically ordered and have less anti site disorders. Upon decreasing the size of rare earth ions, the local structure shows an expansion of NiO6 octahedra and almost unchanged MnO6 octahedra. Xray absorption near edge spectroscopy reveals that majority of Ni and Mn ions are in positive 2 and positive 4 valence states in all the samples. Raman spectra of RNMO show a softening of phonon modes resulting in the elongation of Ni to O and Mn to O bond lengths. Finally, a correlation between lattice parameters, structural distortion, octahedral tilting, superexchange angle, and electronic band gap, Curie temperature, and the rare earth ionic radius is established.
ISSN:2331-8422