Magnetic interactions in a Cu-containing heterospin polymer

Postnikov, A. V.; Галахов, А. В.; Blügel, Stefan

doi:10.1080/01411590500288692

Cited by 10 publications

(12 citation statements)

References 23 publications

(30 reference statements)

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“…The first band structure DFT calculation of exchange coupling constant for a "breathing crystal" compound was performed in Ref. 15 within the SIESTA package 16 only for one temperature point. In recent work 17 a simple GGA+U method in rotationally invariant version by Dudarev et al 18 was employed.…”

Section: -mentioning

confidence: 99%

Exchange coupling transformations in Cu (II) heterospin complexes of “breathing crystals” under structural phase transitions

2015

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Family of "breathing crystals" is the polymer-chain complexes of Cu(hfac) 2 with nitroxides. The polymer chains consist of one-, two-or three-spin clusters. The "breathing crystals" experience simultaneous magnetic and Jahn-Teller type structural phase transitions with change of total cluster spin and drastic change of bond lengths (ca. 10-12%). For the first time the intra-cluster magnetic couplings in "breathing crystals" have been calculated both by band structure methods GGA+U and hybrid DFT (B3LYP and PBE0) for the isolated exchange clusters. The temperature dependence of the magnetic coupling constant was calculated for two polymer-chain compounds of the "breathing crystal" family -C 21 H 19 CuF 12 N 4 O 6 with the chains containing two-spin clusters and C 22 H 21 CuF 12 N 4 O 6 with the chains of alternating three-spin clusters and one-spin sites. It was found that adding a Hubbard-like parameter not only to the copper 3d electrons but also to the oxygen 2p electrons (GGA+U d +U p approach) results in an improved description of exchange coupling in the "breathing crystal" compounds. At the same time treatment of the isolated clusters by a large basis hybrid DFT with high computational cost provides a similar quality fit of the experimental magneto-chemical data as that for the GGA+U d +U p band structure calculation scheme. Our calculations also showed that in spite of the abrupt transformation of the magnetic coupling constant under the phase transition, the band gap in the "breathing crystals" remains about the same value with temperature decrease. C 2015 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.

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Section: -mentioning

confidence: 99%

Exchange coupling transformations in Cu (II) heterospin complexes of “breathing crystals” under structural phase transitions

2015

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“…This difference results in another organization of the polymer chain: In the case considered in Ref. 21 the chain of the exchange clusters has "head-to-head" coupling of the ligands to the magnetic Cu atoms embedded in (hfac) 2 blocks, while in the present case the chain motif is "head-to-tail. "…”

Section: Previous Calculations Of the Breathing Crystalsmentioning

confidence: 82%

“…21 the corresponding chain contains a "three spin-isolated spin" structure, while in the case considered in the present paper the chain is composed of two spin clusters. This results in different magnetic properties.…”

Section: Previous Calculations Of the Breathing Crystalsmentioning

confidence: 96%

“…21, where the spin densities and the magnetic moments of a heterospin compound based Cu(II) hexafluoroacetylacetonate [Cu(hfac) 2 …”

Section: Previous Calculations Of the Breathing Crystalsmentioning

confidence: 99%

“…It should also be mentioned that in Ref. 21 only a high-temperature phase of the crystal was calculated. At the same time, both hightemperature and especially low-temperature phase represent a great interest for study of phase transitions.…”

Section: Previous Calculations Of the Breathing Crystalsmentioning

confidence: 99%

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Interplay between lattice, orbital, and magnetic degrees of freedom in the chain-polymer Cu(II) breathing crystals

et al. 2013

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The chain-polymer Cu(II) "breathing crystals" C 21 H 19 CuF 12 N 4 O 6 were studied using the x-ray diffraction and ab initio band structure calculations. We show that the crystal structure modification at T = 146 K, associated with the spin crossover transition, induces the changes of the orbital order in half of the Cu sites. This in turn results in the switch of the magnetic interaction sign in accordance with the Goodenough-Kanamori-Andersen theory of the coupling between the orbital and spin degrees of freedom.

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Breathing Crystals from Copper Nitroxyl Complexes

Овчаренко

Bagryanskaya

2013

Spin‐Crossover Materials

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IntroductionCoordination chemistry of transition metals with stable nitroxides is one of the actively developed branches of modern chemistry which is an important tool in solving the problems of molecular magnetism. The results of studies of metal complexes with nitroxides and their synthesis have been reported from various viewpoints in monographs and reviews. 1-19 Studies of heterospin compounds have led to the creation of new classes of compounds with new combinations of physical characteristics. 19 These include breathing crystals based on Cu(II) coordination compounds with stable nitroxides. Interest in these compounds has recently developed enormously and their number has increased dramatically. This prompted us to summarize data on their magnetostructural correlations. The discussion concentrated on Cu(II) hexafluoroacetylacetonate complexes [Cu(hfac) 2 ] with pyrazolyl-substituted nitronyl nitroxides. These compounds have been studied for more than 10 years 20, 21 and are well defined. The first part of the chapter summarizes the main features of breathing crystals, obtained using X-ray and magnetic measurements, and the second part overviews the results of EPR. EPR spectroscopy as applied to breathing crystals has a number of peculiarities which demands the development of new approaches. EPR study of breathing crystals is very informative, even though the exchange interaction in nitroxide-copper-nitroxide clusters significantly exceeds the value of Zeeman interaction.A very interesting characteristic of the complexes is the similarity of their magnetic properties to spintransitions in classical systems based on the temperature dependence of the effective magnetic moment (μ eff ). Note that the classical spin-crossover 22-35 is absolutely impossible in Cu(II) complexes with diamagnetic ligands, which contain only d 9 paramagnetic centers. The main distinction of spin-transitions in Cu(II) Spin-Crossover Materials: Properties and Applications, First Edition. Edited by Malcolm A. Halcrow.

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Magnetic interactions in a Cu-containing heterospin polymer

Cited by 10 publications

References 23 publications

Exchange coupling transformations in Cu (II) heterospin complexes of “breathing crystals” under structural phase transitions

Exchange coupling transformations in Cu (II) heterospin complexes of “breathing crystals” under structural phase transitions

Interplay between lattice, orbital, and magnetic degrees of freedom in the chain-polymer Cu(II) breathing crystals

Breathing Crystals from Copper Nitroxyl Complexes

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