TY  - JOUR
AU  - Stojadinović, Bojan
AU  - Đokić, Dejan M.
AU  - Paunović, Novica
AU  - Živković, Ivica
AU  - Ćirić, Luka
AU  - Kusigerski, Vladan
AU  - Dohčević-Mitrović, Zorana
PY  - 2021
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/9956
AB  - We report on temperature dependence of two-phonon Raman spectra in BiFeO3 nanocrystals, above and below the Néel temperature TN using a resonant laser excitation line (λ=532 nm). Two-phonon modes exhibited anomalous frequency hardening and deviation from the anharmonic decay below TN. Such behavior strongly supported the existence of spin-two-phonon interaction, because these modes are known to be very sensitive to the antiferromagnetic ordering. Within the mean-field theory for the nearest-neighbor interaction, the linear relationship between spin–spin correlation function and observed two-phonon frequency shift below TN was obtained. This approach enabled to quantify the spin–phonon interaction by spin–phonon coupling strength for both two-phonon modes and justified the application of mean-field approach. Magnetic measurements revealed the coexistence of antiferromagnetic and weak ferromagnetic phases below TN, which were found non competitive, additionally supporting the mean-field approach from which we deduced that the two-phonon modes in BiFeO3 are correlated with antiferromagnetic ordering below TN.
T2  - Materials Science and Engineering: B
T1  - Unvailing the spin–phonon coupling in nanocrystalline BiFeO3 by resonant two-phonon Raman active modes
VL  - 274
SP  - 115444
DO  - 10.1016/j.mseb.2021.115444
ER  - 

@article{
author = "Stojadinović, Bojan and Đokić, Dejan M. and Paunović, Novica and Živković, Ivica and Ćirić, Luka and Kusigerski, Vladan and Dohčević-Mitrović, Zorana",
year = "2021",
abstract = "We report on temperature dependence of two-phonon Raman spectra in BiFeO3 nanocrystals, above and below the Néel temperature TN using a resonant laser excitation line (λ=532 nm). Two-phonon modes exhibited anomalous frequency hardening and deviation from the anharmonic decay below TN. Such behavior strongly supported the existence of spin-two-phonon interaction, because these modes are known to be very sensitive to the antiferromagnetic ordering. Within the mean-field theory for the nearest-neighbor interaction, the linear relationship between spin–spin correlation function and observed two-phonon frequency shift below TN was obtained. This approach enabled to quantify the spin–phonon interaction by spin–phonon coupling strength for both two-phonon modes and justified the application of mean-field approach. Magnetic measurements revealed the coexistence of antiferromagnetic and weak ferromagnetic phases below TN, which were found non competitive, additionally supporting the mean-field approach from which we deduced that the two-phonon modes in BiFeO3 are correlated with antiferromagnetic ordering below TN.",
journal = "Materials Science and Engineering: B",
title = "Unvailing the spin–phonon coupling in nanocrystalline BiFeO3 by resonant two-phonon Raman active modes",
volume = "274",
pages = "115444",
doi = "10.1016/j.mseb.2021.115444"
}

Stojadinović, B., Đokić, D. M., Paunović, N., Živković, I., Ćirić, L., Kusigerski, V.,& Dohčević-Mitrović, Z.. (2021). Unvailing the spin–phonon coupling in nanocrystalline BiFeO3 by resonant two-phonon Raman active modes. in Materials Science and Engineering: B, 274, 115444.
https://doi.org/10.1016/j.mseb.2021.115444

Stojadinović B, Đokić DM, Paunović N, Živković I, Ćirić L, Kusigerski V, Dohčević-Mitrović Z. Unvailing the spin–phonon coupling in nanocrystalline BiFeO3 by resonant two-phonon Raman active modes. in Materials Science and Engineering: B. 2021;274:115444.
doi:10.1016/j.mseb.2021.115444 .

Stojadinović, Bojan, Đokić, Dejan M., Paunović, Novica, Živković, Ivica, Ćirić, Luka, Kusigerski, Vladan, Dohčević-Mitrović, Zorana, "Unvailing the spin–phonon coupling in nanocrystalline BiFeO3 by resonant two-phonon Raman active modes" in Materials Science and Engineering: B, 274 (2021):115444,
https://doi.org/10.1016/j.mseb.2021.115444 . .

TY  - JOUR
AU  - Ciric, Luka
AU  - Đokić, Dejan M.
AU  - Jacimovic, Jacim
AU  - Sienkiewicz, Andrzej
AU  - Magrez, Arnaud
AU  - Forro, Laszlo
AU  - Šljivančanin, Željko
AU  - Lotya, Mustafa
AU  - Coleman, Jonathan N.
PY  - 2012
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/4858
AB  - Magnetic properties of a large assembly of ultrathin graphitic particles obtained by heavy sonication of graphite powder dispersed in N-methylpyrrolidone were measured by electron-spin resonance (ESR). The ESR signal was decomposed into one narrow and one broad component. The narrow component was associated with localized Curie-type defects. The temperature dependence of the predominant broad component points to a transition to a superparamagnetic-like state at 25 K. By performing the density-functional-theory calculations for graphene with selected extended defects (the sheet edges, zigzag chains of chemisorbed H atoms, and pentagon-octagon rows), we found considerable magnetic moments at C atoms in their vicinities. We attribute the magnetism in the graphitic particles to the localized electronic states near the defects in the network of the p electrons of graphene. The ferromagnetic (FM) correlations among magnetic moments at carbon atoms near the edges are not able to give rise to a long-range FM order.
T2  - Physical Review B: Condensed Matter and Materials Physics
T1  - Magnetism in nanoscale graphite flakes as seen via electron spin resonance
VL  - 85
IS  - 20
DO  - 10.1103/PhysRevB.85.205437
ER  - 

@article{
author = "Ciric, Luka and Đokić, Dejan M. and Jacimovic, Jacim and Sienkiewicz, Andrzej and Magrez, Arnaud and Forro, Laszlo and Šljivančanin, Željko and Lotya, Mustafa and Coleman, Jonathan N.",
year = "2012",
abstract = "Magnetic properties of a large assembly of ultrathin graphitic particles obtained by heavy sonication of graphite powder dispersed in N-methylpyrrolidone were measured by electron-spin resonance (ESR). The ESR signal was decomposed into one narrow and one broad component. The narrow component was associated with localized Curie-type defects. The temperature dependence of the predominant broad component points to a transition to a superparamagnetic-like state at 25 K. By performing the density-functional-theory calculations for graphene with selected extended defects (the sheet edges, zigzag chains of chemisorbed H atoms, and pentagon-octagon rows), we found considerable magnetic moments at C atoms in their vicinities. We attribute the magnetism in the graphitic particles to the localized electronic states near the defects in the network of the p electrons of graphene. The ferromagnetic (FM) correlations among magnetic moments at carbon atoms near the edges are not able to give rise to a long-range FM order.",
journal = "Physical Review B: Condensed Matter and Materials Physics",
title = "Magnetism in nanoscale graphite flakes as seen via electron spin resonance",
volume = "85",
number = "20",
doi = "10.1103/PhysRevB.85.205437"
}

Ciric, L., Đokić, D. M., Jacimovic, J., Sienkiewicz, A., Magrez, A., Forro, L., Šljivančanin, Ž., Lotya, M.,& Coleman, J. N.. (2012). Magnetism in nanoscale graphite flakes as seen via electron spin resonance. in Physical Review B: Condensed Matter and Materials Physics, 85(20).
https://doi.org/10.1103/PhysRevB.85.205437

Ciric L, Đokić DM, Jacimovic J, Sienkiewicz A, Magrez A, Forro L, Šljivančanin Ž, Lotya M, Coleman JN. Magnetism in nanoscale graphite flakes as seen via electron spin resonance. in Physical Review B: Condensed Matter and Materials Physics. 2012;85(20).
doi:10.1103/PhysRevB.85.205437 .

Ciric, Luka, Đokić, Dejan M., Jacimovic, Jacim, Sienkiewicz, Andrzej, Magrez, Arnaud, Forro, Laszlo, Šljivančanin, Željko, Lotya, Mustafa, Coleman, Jonathan N., "Magnetism in nanoscale graphite flakes as seen via electron spin resonance" in Physical Review B: Condensed Matter and Materials Physics, 85, no. 20 (2012),
https://doi.org/10.1103/PhysRevB.85.205437 . .

TY  - JOUR
AU  - Đokić, Dejan M.
AU  - Popović, Zoran V.
AU  - Vukajlović, Filip R.
PY  - 2008
UR  - https://vinar.vin.bg.ac.rs/handle/123456789/3357
AB  - The effects of spin-phonon interaction and magnetic anisotropy on the temperature dependence of the infrared optical phonon modes in the antiferromagnetic alpha-MnSe are investigated by use of Greens function formalism within 1/z perturbation framework. The renormalization effects are calculated explicitly as a function of temperature, phonon-phonon, and spin-phonon interaction constants. Temperature dependence of the renormalized LO phonon frequencies of the F(1u) infrared active and combinational phonon modes are calculated and compared with experimental data. We have shown that the inclusion of anisotropy is necessary in order to get a good quantitative agreement with the experiment.
T2  - Physical Review B: Condensed Matter and Materials Physics
T1  - Influence of antiferromagnetic spin ordering on the far-infrared active optical phonon modes of alpha-MnSe
VL  - 77
IS  - 1
DO  - 10.1103/PhysRevB.77.014305
ER  - 

@article{
author = "Đokić, Dejan M. and Popović, Zoran V. and Vukajlović, Filip R.",
year = "2008",
abstract = "The effects of spin-phonon interaction and magnetic anisotropy on the temperature dependence of the infrared optical phonon modes in the antiferromagnetic alpha-MnSe are investigated by use of Greens function formalism within 1/z perturbation framework. The renormalization effects are calculated explicitly as a function of temperature, phonon-phonon, and spin-phonon interaction constants. Temperature dependence of the renormalized LO phonon frequencies of the F(1u) infrared active and combinational phonon modes are calculated and compared with experimental data. We have shown that the inclusion of anisotropy is necessary in order to get a good quantitative agreement with the experiment.",
journal = "Physical Review B: Condensed Matter and Materials Physics",
title = "Influence of antiferromagnetic spin ordering on the far-infrared active optical phonon modes of alpha-MnSe",
volume = "77",
number = "1",
doi = "10.1103/PhysRevB.77.014305"
}

Đokić, D. M., Popović, Z. V.,& Vukajlović, F. R.. (2008). Influence of antiferromagnetic spin ordering on the far-infrared active optical phonon modes of alpha-MnSe. in Physical Review B: Condensed Matter and Materials Physics, 77(1).
https://doi.org/10.1103/PhysRevB.77.014305

Đokić DM, Popović ZV, Vukajlović FR. Influence of antiferromagnetic spin ordering on the far-infrared active optical phonon modes of alpha-MnSe. in Physical Review B: Condensed Matter and Materials Physics. 2008;77(1).
doi:10.1103/PhysRevB.77.014305 .

Đokić, Dejan M., Popović, Zoran V., Vukajlović, Filip R., "Influence of antiferromagnetic spin ordering on the far-infrared active optical phonon modes of alpha-MnSe" in Physical Review B: Condensed Matter and Materials Physics, 77, no. 1 (2008),
https://doi.org/10.1103/PhysRevB.77.014305 . .