Low-frequency spin dynamics in the orthorhombic phase of La2CuO4

Abstract

Abstract. An effective field theory is derived that describes the low-frequency spin dynamics in the low-temperature orthorombic phase of La2CuO4. Restricted to a single CuO2 layer the effective theory is a simple generalization of the relativistic nonlinear σ model to include all spin interactions allowed by symmetry. Incorporating a weak interlayer interaction leads to two coupled nonlinear σ models which provide an efficient description of the complete bilayer dynamics. Particular attention is paid to the weak-ferromagnetic and spin-flop transitions induced by external magnetic fields. The main features of the observed (covert) weak ferromagnetism are thus accounted for in a straightforward manner but some of the finer theoretical predictions would require further experimental investigation. The derived framework is also suitable for the study of the structure and dynamics of magnetic domains in undoped La2CuO4.PACS. 75.10.-b General theory and models of magnetic ordering − 74.72.Dn. La -based cuprates

Width of the longitudinal magnon in the vicinity of the O(3) quantum critical point

“…A derivation of this term within the effective field theory can be found in Ref. 28. With account of the anisotropy, the triple degeneracy of the dispersion in the magnetically disordered phase, p < p c , is lifted, the z and y modes have the same dispersion (6) as before while the x mode has a higher energy,…”

Intermediate phase in the spiral antiferromagnetBa2CuGe2O7Chovan1, Papanicolaou2, Komineas3 2002Phys. Rev. BSelf Cite314540View full textAdd to dashboardCite

“…Nevertheless, the relevant low-energy dynamics can be efficiently calculated in terms of a continuum field theory which provides a reasonable approximation for Ba 2 CuGe 2 O 7 because the period of the observed spiral is equal to about 37 lattice constants along the x-direction. A similar approach is often invoked in the related subject of weak ferromagnetism 12,13 and can be implemented by a straightforward step-by-step procedure starting from the original discrete Hamiltonian 14,15 .…”

“…(2.15) is absent from the energy functional of Zheludev et al 5 . A contribution of that nature is present in the early work of Andreev and Marchenko 12 and plays a significant role in various aspects of weak ferromagnetism 15 . This term vanishes when the field is applied along the c-axis (h × d z = 0) and thus does not affect the analysis of the CI transition.…”

Lightly DopedLa2−xSrxCuO4as a Lifshitz Helimagnet

“…The model.-The presence of static magnetic correlations within the SG phase of LSCO allows us to use a Hamiltonian description of the long-wavelength fluctuations of the staggered order parameter n (see [12,13] for a detailed derivation of the model). For x 0, we can write (we use a soft version of the n 2 1 constraint)…”