scholarly journals Hydrodynamic theory of magnets with strong exchange interaction

1997 ◽  
Vol 23 (7) ◽  
pp. 522-533 ◽  
Author(s):  
A. A. Isayev ◽  
M. Yu. Kovalevsky ◽  
S. V. Peletminsky

The paramagnetic resonance method has been applied to investigate the magnetic properties of complexes containing elements of the 4 d and 5 d groups. It is shown that the resonance results, and such information as is available from susceptibility measurements, can be accounted for to a good approximation by assuming that there are either covalent σ -bonds or very strong electrostatic bonds in the complex (Van Vleck 1935). In the case of d 5 complexes, however, accurate measurements of the spectroscopic splitting factors show small discrepancies with this theory. Furthermore, an anomalous hyperfine structure is observed for the complex [IrCl 6 ] 2- , which displays lines arising not only from the Ir nucleus, but also from the surrounding Cl nuclei. These effects are ascribed to the presence of weak π -bonds, in addition to σ -bonds, in the complex (Stevens 1953). In magnetically concentrated salts of the 5 d group, it is found that there is strong exchange interaction between paramagnetic neighbours.


2006 ◽  
Vol 110 (7) ◽  
pp. 2315-2317 ◽  
Author(s):  
Matvey V. Fedin ◽  
Sergey L. Veber ◽  
Igor A. Gromov ◽  
Victor I. Ovcharenko ◽  
Renad Z. Sagdeev ◽  
...  

2020 ◽  
Vol 56 (16) ◽  
pp. 2447-2450
Author(s):  
Youki Sumiya ◽  
Kenji Higashiguchi ◽  
Kenji Matsuda

Bis(imino nitroxide) bridged by a diarylethene annulated isomer was found to show a strong exchange interaction, suggesting the use of the annulated isomer as a highly-conductive molecular wire.


2018 ◽  
Vol 74 (11) ◽  
pp. 1469-1476
Author(s):  
Ivan Potočňák ◽  
Oleksandr Bukrynov ◽  
Katarína Ráczová ◽  
Erik Čižmár ◽  
Svitlana Vitushkina ◽  
...  

From the system CuCl2–biq–NaN(CN)2 (biq is 2,2′-biquinoline), the binuclear molecular complex bis(μ-dicyanamido-κ2 N 1:N 5)bis[(2,2′-biquinoline-κ2 N,N′)(dicyanamido-κN 1)copper(II)], [Cu2(C2N3)4(C18H12N2)2] or [Cu2(biq)2(dca)2(μ1,5-dca)2] (1) [dca is dicyanamide, N(CN)2 −] was isolated and characterized by crystal structure analysis, and spectral, thermal and magnetic measurements. IR spectroscopy confirmed the presence of the biq and dca ligands in 1. Its solid-state structure consists of discrete centrosymmetric binuclear copper(II) units with double end-to-end dca bridges. Each CuII atom is in a distorted square-pyramidal environment with the equatorial plane formed by two nitrile N atoms from bridging dca groups, one of the two N atoms of the chelate biq molecule and one nitrile N atom from a terminal dca ligand, whereas the second biq N atom occupies the axial position. Thermal decomposition of 1 in an air atmosphere proceeds gradually, with copper(I) cyanide being the final decomposition product. Magnetic measurements revealed the formation of alternating spin chains and a relatively strong exchange interaction within the binuclear units was also confirmed by Broken Symmetry DFT (density functional theory) calculations.


2021 ◽  
Author(s):  
Shabir Ahmad Mir ◽  
Dinesh C. Gupta

Abstract Through the conventional DFT computation, we have designed new oxide double perovskites Ba2BNiO6 (B = Fe and Co). The structural and thermodynamic stabilities are defined by optimizing the crystal energy and determination of tolerance factor and cohesive energies. Thereafter, at the optimized lattice constant, we have explored the different physical properties. The GGA+mBJ electronic band-structure depicts the semiconducting nature for Ba2CoNiO6 while half-metallic with 100% spin polarization for Ba2FeNiO6. The origin of such a diverse band profile upon changing Fe to Co is explained with the help of the orbital diagram and exchange interaction. The eg-eg interaction is strong in these perovskites compared to eg-t2g and t2g-t2g hybridization. The strong exchange interaction among eg states via O-p states happens because the B-O-Ni angle is strictly 180°. Furthermore, due to the narrow bandgaps, we have explored the transport properties to express the applicability of these materials towards thermoelectric technology. Also, herein we have investigated the dependency of transport properties on band profile. The semiconducting nature in Ba2CoNiO6 results in a high ZT~0.8 at room temperature makes it suitable for energy restoration.


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