scholarly journals Anomaly in structural noncentrosymmetry around TN n bulk and nanoscale BiFeO3

2013 ◽  
Vol 28 (S2) ◽  
pp. S94-S105 ◽  
Author(s):  
Sudipta Goswami ◽  
Dipten Bhattacharya ◽  
Gail N. Iles ◽  
Barnali Ghosh ◽  
Anastasiia A. Prytuliak ◽  
...  
Keyword(s):  
High Resolution ◽  
Transition Point ◽  
Magnetic Transition ◽  
Bulk Sample ◽  
Neutron Diffraction Data ◽  
Powder Neutron Diffraction ◽  
Sensor Devices ◽  
Higher Temperature ◽  
Powder Neutron Diffraction Data ◽  
Application Prospects

Using high resolution powder neutron diffraction data, we show that there is a distinct anomaly in the structural noncentrosymmetry around the magnetic transition point TN for bulk and nanoscale BiFeO3. It appears that the structural noncentrosymmetry - which gives rise to the ferroelectric polarization - is suppressed anomalously by ~1% (of the average noncentrosymmetry at above the magnetic transition) in the bulk sample and by ~12% in the nanoscale sample as the magnetic transition is approached from higher temperature. This observation shows that the multiferroic coupling improves in the nanoscale sample which is expected to brighten the application prospects of nanoscale BiFeO3 in nanospintronics-based sensor devices.PACS Nos. 75.70.Cn, 75.75.-c

Site occupancy in gamma alumina

1996 ◽  
Vol 54 ◽  
pp. 654-655
Author(s):  
C. A. Bateman ◽  
A.Z. Ringwelski ◽  
R.W. Broach
Keyword(s):  
Spinel Structure ◽  
Site Occupancy ◽  
Unit Cell ◽  
Neutron Diffraction Data ◽  
Gamma Alumina ◽  
Tetrahedral Sites ◽  
Powder Neutron Diffraction ◽  
Cation Sites ◽  
Powder Neutron Diffraction Data ◽  
Insufficient Number

Gamma (γ) alumina is referred to as a defect spinel because it has a tetragonally distorted spinel structure (AB2O4) and an insufficient number of cations to fill all cation sites. In the spinel structure, the oxygen lattice is cubic close packed with A- and B-site cations in tetrahedral and octahedral coordination, respectively. The 2l⅓ Al atoms per unit cell of γ alumina can distribute themselves across 16 octahedral and 8 tetrahedral sites.The literature differs on where the 2⅔ cation vacancies per unit cell are located. Wilson and McConnell proposed that the vacancies in γ alumina, as first formed by calcining boehmite, are predominantly on the tetrahedral lattice but, with further heat treatment, move to occupy random positions on both octahedral and tetrahedral lattices. One study using NMR showed that the vacancies lay exclusively on the tetrahedral lattice, independent of the calcination temperature. A more-recent study using Rietveld refinement of powder neutron diffraction data suggested that both octahedral and tetrahedral lattices were partially occupied.

Commensurate and Incommensurate Oxide Structures Related to 2H Perovskite

1998 ◽  
Vol 547 ◽  
Author(s):  
P. D. Battle ◽  
G.R. Blake ◽  
J.C. Burley ◽  
E. J. Cussen ◽  
J. Sloan ◽  
...  
Keyword(s):  
Neutron Diffraction ◽  
Diffraction Data ◽  
Nearest Neighbour ◽  
Neutron Diffraction Data ◽  
Magnetic Structures ◽  
Powder Neutron Diffraction ◽  
Powder Neutron Diffraction Data

AbstractThe magnetic structures of Ca3LiRuO6 and Ca3NaRuO6 have been deduced from powder neutron diffraction data. In each case successive Ru5+ cations in the [001] chains of the Sr4PtO6-like structure are antiferromagnetically coupled, and nearest-neighbour Ru5+ cations in adjacent chains are also antiferromagnetically coupled.

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