Berlin 2015 – scientific programme
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MA: Fachverband Magnetismus
MA 19: POSTER Ia
MA 19.2: Poster
Tuesday, March 17, 2015, 09:30–13:00, Poster A
Thermodynamics of the frustrated J1-J2 Heisenberg ferromagnet on a BCC lattice with arbitrary spin — •Patrick Müller1, Johannes Richter1, Andreas Hauser1, and Dieter Ihle2 — 1Institut für Theoretische Physik, Otto-von-Guericke-Universität Magdeburg, D-39016 Magdeburg, Germany — 2Institut für Theoretische Physik, Universität Leipzig, D-04109 Leipzig, Germany
The so-called J1-J2 models with competing nearest-neighbor (J1) and next-nearest-neighbor (J2) couplings are canonical models to study frustration effects in magnetic systems. Such models have been widely studied in low dimensions, see, e.g. [1]. In the present study we investigate the influence of frustration on the thermodynamic properties of the J1-J2 spin-S ferromagnet (J1=−1, J2>0) on the BCC lattice. We use a second order Green’s function (GF) approach to calculate the spin-wave spectrum, the Curie temperature TC, the magnetization, the specific heat, the susceptibility and the magnetic correlation length. We complement our GF results with data from a high-temperature expansion [2]. Both methods are used to determine TC as a function of the frustration parameter J2 and the spin quantum number S and derive empirical formulas for TC(J2,S). We find that TC vanishes at a critical value J2c that is very close to the classical transition point J2c,clas=2/3. [1] M. Härtel, J. Richter, D. Ihle, and S.-L. Drechsler, Phys. Rev. B 81, 174421 (2010); M. Härtel, J. Richter, O. Götze, D. Ihle and S.-L. Drechsler, Phys. Rev. B 87, 054412 (2013). [2] A. Lohmann, H.-J. Schmidt and J. Richter, Phys. Rev. B 89, 014415 (2014).