Magnetic structure of molecular magnet Fe[Fe(CN)₆]·4H₂O

We have studied the magnetic structure of Fe[Fe(CN)6]·4H2O, prepared by precipitation method, using neutron diffraction technique. Temperature dependent DC magnetization study down to 4.2 K shows that the compound undergoes from a high temperature disordered (paramagnetic) to an ordered magnetic phase transition at 22.6 K. Rietveld analysis of neutron diffraction pattern at 60 K (in its paramagnetic phase) revealed a face centred cubic structure with space group Fm3m. The structure contains three-dimensional network of straight Fe3+-C≡N-Fe3+ chains along the edges of the unit cell cube. Fe3+ ions occupy 4a (0, 0, 0) and 4b (1/2, 1/2, 1/2) positions. Fe3+(0, 0, 0) is surrounded octahedrally by six nitrogen atoms and Fe3+ (1/2, 1/2, 1/2) is surrounded octahedrally by six carbon atoms. Magnetic Rietveld refinement of neutron diffraction data at 11 K shows a ferromagnetic coupling between the two inequivalent Fe3+ sites. Refinement yielded an ordered moment of 4.4(6) and 0.8(6) μB per Fe ion located at (0, 0, 0) and (1/2, 1/2, 1/2), respectively. Ordered moments are found to align along the face diagonal. The observed net moment from low temperature neutron diffraction study is consistent with DC magnetization results

Long-range and short-range magnetic correlations, and microscopic origin of net magnetization in the spin-1 trimer chain compound CaNi3P4O14

Spin-spin correlations and microscopic origin of net magnetization in the spin-1 trimer chain compound CaNi3P4O14 have been investigated by powder neutron diffraction. The present study reveals a 3D long-range magnetic ordering below 16 K where the magnetic structure consists of ferromagnetic trimers that are coupled ferromagnetically along the spin-chain. The moment components along the a and c axes arrange antiferromagnetically. Our study establishes that the uncompensated moment components along the b axis result in a net magnetization per unit cell. The magnetic structure, determined in the present study, is in agreement with the results of recent first principles calculation; however, it is in contrast to a fascinating experimental prediction of ferrimagnetic ordering based on the periodicity of the exchange interactions in CaNi3P4O14. Our study also confirms the presence of broad diffuse magnetic scattering, due to 1D short-range spin-spin correlations, over a wide temperature range below ~50 K down to a temperature well below the Tc. Total neutron scattering analysis by the RMC method reveals that the dominating spin-spin correlation above Tc is ferromagnetic and along the b axis. The nearest neighbour spin-spin correlations along the a and c axes are found to be weakly antiferromagnetic. The nature of the trimer spin structure of the short-range state is similar to that of the 3D long-range ordered state. The present investigation of microscopic nature of the magnetic ground state also explains the condition required for the 1/3 magnetization plateau to be observed in the trimer spin-chains. In spite of the S=1 trimer chain system, the present compound CaNi3P4O14 is found to be a good realization of 3D magnet below the Tc=16 K with full ordered moment values of ~2 mu_B/Ni2+ (1.98 and 1.96 mu_B/Ni2+ for two Ni sites, respectively) at 1.5 K.Comment: 10 pages, 8 figure

To study outcome of surgical management of distal 3rd and proximal 3rd fractures of tibia in adults using expert tibial nails

Background: Tibia is most commonly fractured long bone. Within few years population of India and number of vehicles has increased very much. This has lead to manifold increase in not only rate of tibia fracture but also in complexity of fracture. Using interlocking nail in tibial fracture with short proximal and distal fragment render it unstable leading to frequent loss of reduction causing malunion. Multidirectional interlocking screws ensure that alignment can be well maintained and stability preserved in short proximal or distal tibial segments.Methods: A prospective, non randomized study was conducted comprising of 30 patients of proximal and distal 1/3rd fracture of tibia in, Department of Orthopaedics, Bokaro General Hospital. The method used for fracture fixation was open/closed reduction and internal fixation with expert tibial nail. The duration of study was June 2013 to June 2016. The data thus obtained was evaluated in terms of mode of injury, associated injury, fracture pattern, etc. Also outcome was measured and complication were evaluated and treated. Functional outcome was evaluated using hospital for special surgery (HSS) knee score.Results: All 30 patient were followed up successfully during period of 3 years. The mean duration of radiological union in this study was 20.6 weeks, though it ranged from 18 to 26 weeks. 8 patients developed some complication in form of superficial infection, malunion etc but none of the patient had non-union of fractured bone. On the basis of hospital for special surgery (HSS) knee score13 patients had excellent results; 9 had good results, 05 had fair results and 3 had poor result. Mean HSS knee score was 82.3 (SD 15.3) after 3 years of follow up.Conclusions: Expert tibial interlocking nail is good treatment option for distal and proximal 1/3 fracture of tibia especially in non intra-articular facture. It can be used in simple intra-articular fracture but additional hardware is required