Milan R. Pantic | Searcharxiv

arXiv2013

Phase diagram of spin-$\frac 12$ quantum Heisenberg $J_1-J_2$ antiferromagnet on the body-centered-cubic lattice in random phase approximation

Magnetic properties of spin $\frac 12$ $J_1-J_2$ Heisenberg antiferromagnet on body centered cubic lattice are investigated. By using two-time temperature Green's functions, sublattice magnetization and critical temperature depending on the frustration ratio $p=J_2/J_1$ are obtained in both stripe and Néel phase. The analysis of ground state sublattice magnetization and phase diagram indicates the critical end point at $J_2/J_1 =0.714$, in agreement with previous studies.

cond-mat.str-el↗

arXiv2013

Magnon Energy Renormalization and Low-Temperature Thermodynamics of O(3) Heisenberg Ferromagnets

We present the perturbation theory for lattice magnon fields of $D$-dimensional O(3) Heisenberg ferromagnet. The effective Hamiltonian for the lattice magnon fields is obtained starting from the effective Lagrangian, with two dominant contributions that describe magnon-magnon interactions identified as a usual gradient term for the unit vector field and a part originating in the Wess-Zumino-Witten term of effective Lagrangian. Feynman diagrams for lattice scalar fields with derivative couplings are introduced, on basis of which we investigate the influence of magnon-magnon interactions on magnon self-energy and ferromagnet free energy. We also comment appearance of spurious terms in the low-temperature series for the free energy by examining magnon-magnon interactions and internal symmetry of the effective Hamiltonian (Lagrangian).

cond-mat.str-el↗