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

Streltsov, S. V.; Петрова, М. В.; Morozov, V. A.; Романенко, Г. В.; Анисимов, В. И.; Lukzen, Nikita N.

doi:10.1103/physrevb.87.024425

Cited by 17 publications

(8 citation statements)

References 26 publications

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“…Similar effects were found in many other systems based on the transition metal ions. [26,27] The lowest total energy corresponds to the magnetic configuration, when all Mn ions are ordered ferromagnetically.…”

Section: Results Of the Calculations And Comparison With Experimentsmentioning

confidence: 99%

Nature of the ferromagnetic ground state in the Mn4molecular magnet

et al. 2014

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Using ab initio band structure and model calculations we studied magnetic properties of one of the Mn4 molecular magnets (Mn4(hmp)6), where two types of the Mn ions exist: Mn 3+ and Mn 2+ . The direct calculation of the exchange constants in the GGA+U approximation shows that in contrast to a common belief the strongest exchange coupling is not between two Mn 3+ ions (J bb ), but along two out of four exchange paths connecting Mn 3+ and Mn 2+ ions (J wb ). Within the perturbation theory we performed the microscopic analysis of different contributions to the exchange constants, which allows us to establish the mechanism for the largest ferromagnetic exchange. In the presence of the charge order the lowest in energy virtual excitations, contributing to the superexchange, will be not those across the Hubbard gap ∼ U , but will be those between the Mn 3+ and Mn 4+ ions, which cost much smaller energy V (≪ U ). Together with strong Hund's rule coupling and specific orbital order this leads to large ferromagnetic exchange interaction for two out of four Mn 2+ -Mn 3+pairs.

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Section: Results Of the Calculations And Comparison With Experimentsmentioning

confidence: 99%

Nature of the ferromagnetic ground state in the Mn4molecular magnet

et al. 2014

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“…The GGA+U approximation was used to take the strong Coulomb interaction between the Cu sites into account. The Hund's rule exchange and Coulomb repulsion were chosen to be J H = 0.9 eV and U = 7 eV, respectively [26,27]. The unit cell of Cu 3 Y(SeO 3 ) 2 O 2 Cl contains only one layer of CuO 4 plaquettes.…”

Section: Resultsmentioning

confidence: 99%

Thermodynamic properties, electron spin resonance, and underlying spin model inCu3Y(SeO3)2O2Cl
Zakharov
¹
,
Zvereva
²
,
Berdonosov
³

et al. 2014
Phys. Rev. B
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We report a detailed study of the magnetic properties of the buckled kagome compound Cu 3 Y(SeO 3) 2 O 2 Cl using heat capacity, magnetization, powder neutron diffraction, electron spin resonance and first-principles calculations. The crystal structure is confirmed to be isotypic with the mineral francisite, with orthorhombic space group symmetry Pmmn throughout the temperature range 5-300 K. Magnetization, heat capacity and neutron diffraction confirm long range magnetic order below T N = 35 K. The electron spin resonance spectra reveal the presence of two modes corresponding to two different crystallographic Cu positions. The principal g-values of the g-tensor of Cu(1) sites were found to be g 1 = 2.18(4), g 2 = 2.10(6) and g 3 = 2.05(9), while the effective g-factor of Cu(2) sites is almost isotropic and is on average g = 2.09(5). At low temperatures, Cu 3 Y(SeO 3) 2 O 2 Cl undergoes a metamagnetic transition, with a critical field B C = 2.6 T at 2 K, due to the suppression of the inter-plane exchange interactions and saturates in modest magnetic field, B S  8 T. The first-principles calculations allow an estimation of both intra-plane and inter-plane exchange interactions. The weakness of the inter-plane exchange interaction results in low values of the critical fields for the metamagnetic transition, while the competition between intra-plane exchange interactions of different signs results in a similarly low value of the saturation field.

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“…When integrating in the reciprocal space, we used 2 × 2 × 2 k-points in the Monkhorst-Pack grid [26] in the first Brillouin zone; the Gaussian broadening was chosen to be 0.136 eV. The Hubbard corrections on the copper and oxygen atoms were applied within the framework of the GGA+U scheme with the parameters Ud(Cu) = 9.8 eV and Up(O) = 5.0 eV, respectively [27,28]. In the band DFT approach, combined with the conventional BS method to obtain exchange integrals, we calculated the set of unit cell energies for a complete number of spin polarization states of the crystal unit cell.…”

Section: Density Functional Theory (Dft) Calculationsmentioning

confidence: 99%

Spin Transition in the Cu(hfac)2 Complex with (4-Ethylpyridin-3-yl)-Substituted Nitronyl Nitroxide Caused by the “Asymmetric” Structural Rearrangement of Exchange Clusters in the Heterospin Molecule

et al. 2019

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Methods for the synthesis of binuclear [Cu(hfac)2LEt]2 and tetranuclear [[Cu(hfac)2]4(LEt)2] heterospin compounds based on copper hexafluoroacetylacetonate [Cu(hfac)2] and 2-(4-ethylpyridin-3-yl)-4,5-bis(spirocyclopentyl)-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl (LEt), were developed. The crystals of the complexes are elastic and do not crash during repeated cooling–heating cycles. It was found that a singlet–triplet conversion occurred in all of the {Cu(II)–O•–N<} exchange clusters in the molecules of the binuclear [Cu(hfac)2LEt]2 which led to spin coupling with cooling. The transition occurred in a wide temperature range with a maximum gradient ΔχT at ≈180 K. The structural transformation of the crystals takes place at T < 200 K and is accompanied by the lowering of symmetry from monoclinic to triclinic, twinning, and a considerable shortening of the Cu–ONO distance (2.19 and 1.97 Å at 295 and 50 K, respectively). For the tetranuclear [[Cu(hfac)2]4(LEt)2], two structural transitions were recorded (at ≈154 K and ≈118 K), which led to a considerable change in the spatial position of the Et substituent in the nitronyl nitroxyl fragment. The low-temperature process was accompanied by a spin transition recorded as a hysteresis loop on the χT(T) curve during the repeated cooling–heating cycles (T½↑ = 122 K, T½↓ = 115 K). This transition is unusual because it causes spin coupling in half of all of the {>N–•O–Cu2+} terminal exchange clusters, leading to spin compensation for only two paramagnetic centers of the six centers in the molecule.

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

Cited by 17 publications

References 26 publications

Nature of the ferromagnetic ground state in the Mn4molecular magnet

Nature of the ferromagnetic ground state in the Mn4molecular magnet

Thermodynamic properties, electron spin resonance, and underlying spin model inCu3Y(SeO3)2O2Cl
Zakharov
¹
,
Zvereva
²
,
Berdonosov
³

et al. 2014
Phys. Rev. B
Self Cite
43
3
11
0
View full text Add to dashboard Cite

Spin Transition in the Cu(hfac)2 Complex with (4-Ethylpyridin-3-yl)-Substituted Nitronyl Nitroxide Caused by the “Asymmetric” Structural Rearrangement of Exchange Clusters in the Heterospin Molecule

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

Cited by 17 publications

References 26 publications

Nature of the ferromagnetic ground state in the Mn4molecular magnet

Nature of the ferromagnetic ground state in the Mn4molecular magnet

Thermodynamic properties, electron spin resonance, and underlying spin model inCu3Y(SeO3)2O2ClZakharov1, Zvereva2, Berdonosov3 et al. 2014Phys. Rev. BSelf Cite433110View full textAdd to dashboardCite

Spin Transition in the Cu(hfac)2 Complex with (4-Ethylpyridin-3-yl)-Substituted Nitronyl Nitroxide Caused by the “Asymmetric” Structural Rearrangement of Exchange Clusters in the Heterospin Molecule

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Thermodynamic properties, electron spin resonance, and underlying spin model inCu3Y(SeO3)2O2Cl
Zakharov
¹
,
Zvereva
²
,
Berdonosov
³

et al. 2014
Phys. Rev. B
Self Cite
43
3
11
0
View full text Add to dashboard Cite