Are there Optical Magnons?

• Authors: U. Köbler
• Languages of publication: EN

Abstracts

EN

Optical magnons should occur in magnets containing two in-equivalent magnetic species only. However, Heisenberg interactions between in-equivalent magnetic atoms can be expected to be weak. This is because free exchange of electrons between chemically different magnetic atoms appears not generally possible. To the best of our knowledge optical magnons have never been identified unambiguously experimentally. Confusion is provided by the fact that two magnon branches commonly occur in antiferromagnets with ferromagnetically ordered crystallographic planes and opposite spin orientations from plane to plane. This applies to MnO, EuTe, CoCl₂, Fe₂O₃, K₂FeF₄. Associated with the ferromagnetic planes is a particular low-energy magnon branch. The high-energy magnon branch is the antiferromagnetic branch and not an optical magnon. In Fe₃O₄ (magnetite), weak interactions between the Fe²⁺ moments and the Fe³⁺ moments are evidenced by the fact that the order parameters of the FeO and of the Fe₂O₃ subsystem have different temperature dependencies. The observed two magnon branches can be attributed to the Fe₂O₃ and to the FeO subsystem, respectively. This applies equally to the two observed magnon branches in mixed crystals such as Rb₂Mn_{0.5}Ni_{0.5}F₄, KCo_{0.71}Mn_{0.29}F₃ or Mn_{0.3}Co_{0.7}F₂ that can be understood as modified dispersions of the constituent materials.

Keywords

EN

75.30.Ds; 75.30.Et

Discipline

• 75.30.Ds: Spin waves(for spin-wave resonance, see 76.50.+g)
• 75.30.Et: Exchange and superexchange interactions(see also 71.70.Gm Exchange interactions)

• Publisher: Institute of Physics, Polish Academy of Sciences
• Journal: Acta Physica Polonica A
• Year: 2018
• Volume: 133
• Issue: 3
• Pages: 459-462

Dates

published

2018-03

Contributors

author

U. Köbler

• Research Centre Jülich, Institute PGI, 52425 Jülich, Germany

References

• [1] U. Köbler, Acta Phys. Pol. A 127, 1694 (2015), doi: 10.12693/APhysPolA.127.1694
• [2] K.G. Wilson, J. Kogut, Phys. Rep. 12C, 75 (1974), doi: 10.1016/0370-1573(74)90023-4
• [3] A. Hoser, U. Köbler, Acta Phys. Pol. A 127, 350 (2015), doi: 10.12693/APhysPolA.127.350
• [4] A. Hoser, U. Köbler, J. Physics: Conf. Series 746, 012062 (2016), doi: 10.1088/1742-6596/746/1/012062
• [5] B.V. Karpenko, A.V. Kuznetsov, V.V. Dyakin, J. Magn. Magn. Mater. 117, 317 (1992), doi: 10.1016/0304-8853(92)90087-5
• [6] M.P.H. Thurlings, E. Frikkee, H.W. de Wijn, Phys. Rev. B 25, 4750 (1982), doi: 10.1103/PhysRevB.25.4750
• [7] G. Pepy, J. Phys. Chem. Solids 35, 433 (1974), doi: 10.1016/S0022-3697(74)80037-5
• [8] J. Magarińo, J. Tuchendler, A.R. Fert, J. Gelard, Sol. State Commun. 23, 175 (1977), doi: 10.1016/0038-1098(77)90103-X
• [9] E.J. Samuelsen, G. Shirane, Phys. Status Solidi 42, 241 (1970), doi: 10.1002/pssb.19700420125
• [10] S.O. Demokritov, N.M. Kreines, V.I. Kudinov, Sov. Phys. JETP 65, 389 (1987)
• [11] M.T. Hutchings, J. Phys. C 6, 3143 (1973), doi: 10.1088/0022-3719/6/21/018
• [12] O. Steinsvoll, Physica Scripta 26, 119 (1982), doi: 10.1088/0031-8949/26/2/011
• [13] A.W. McReynolds, T. Riste, Phys. Rev. 95, 1161 (1954), doi: 10.1103/PhysRev.95.1161
• [14] R.J. Birgeneau, L.R. Walker, H.J. Guggenheim, J. Als-Nielsen, G. Shirane, J. Phys. C 8, L328 (1975), doi: 10.1088/0022-3719/8/15/006
• [15] W.J.L. Buyers, T.M. Holden, E.C. Svensson, R.A. Cowley, R.W.H. Stevenson, Phys. Rev. Lett. 27, 1442 (1971), doi: 10.1103/PhysRevLett.27.1442
• [16] W.J.L. Buyers, D.E. Pepper, R.J. Elliott, J. Phys. C 5, 2611 (1972), doi: 10.1088/0022-3719/5/18/011
• [17] U. Köbler, Int. J. Thermodyn. 18, 277 (2015), doi: 10.5541/ijot.5000130678
• [18] U. Köbler, A. Hoser, J.-U. Hoffmann, Physica B 382, 98 (2006), doi: 10.1016/j.physb.2006.02.007

Identifiers

DOI

10.12693/APhysPolA.133.459