Electron-spin resonance in spin-1 planar magnetic chains

Abstract

We present a theoretical study of electron-spin resonance ͑ESR͒ in spin-1 chains with a strong planar anisotropy and an exchange interaction that is either ferromagnetic or antiferromagnetic. For a sufficiently weak bias field, the ground state carries vanishing azimuthal spin and the resonance spectrum is dominated by transitions to excitons and antiexcitons with azimuthal spin Ϯ1. When the field exceeds a certain critical value, the ground state is a fully saturated ferromagnet and the relevant elementary excitations are ordinary magnons. The contribution of a two-magnon bound state, often referred to as the single-ion bound state, is of special importance and is analyzed in detail. These theoretical results are consistent with available ESR measurements on Ni͑C 2 H 8 N 2 ͒ 2 Ni͑CN͒ 4 and suggest more detailed experiments. ͓S0163-1829͑97͒05438-6͔

Resonance absorption, reflection, transmission of phonons and heat transfer through interface between two solids

“…Fano resonance is expected whenever a set of discrete states is mixed with continuum spectrum. Exactly this situation was predicted in the theoretical work [28] for spin-1 magnetic chains with a strong planar anisotropy and an exchange that is either ferromagnetic or antiferromagnetic. Energetic spectrum of these chains consists of three excitation branches approximately in the same energetic domain of magnon dispersion curve, two-magnon continuum and single-ion bound states.…”

EffectiveS=12description of theS=1chain with strong easy-plane anisotropy

“…The original experiment was repeated in Ref. [10] in order to clarify certain important features predicted by theory [5] such as the occurrence of a two-magnon bound state for strong fields in the region H > H 2 . One of the main conclusions of the above references is that the essential features of the ESR spectrum observed in DTN are accounted for by the strictly 1D S = 1 model (1).…”

“…At this point level crossing occurs and the azimuthal spin of the ground state is no longer zero but increases with increasing field. The value of H 1 is defined by the gap ∆ 0 , H 1 = ∆ 0 , for which a third-order approximation is given by [5] A second transition occurs at a critical field H 2 , above which the ground state is fully polarized and the gapped excitation spectrum of a magnon can be calculated exactly. The value of H 2 is defined by the lowest gap of the magnon dispersion:…”

Magnetic Excitations in the Spin-1 Anisotropic Heisenberg Antiferromagnetic Chain SystemNiCl2−4SC(NH2)2

“…While the underlying physics of Haldane chains is fairly well understood, relatively little is known about the magnetic properties (and particularly the elementary excitation spectrum) of nonHaldane S = 1 AFM chains in the large-D phase. Intense theoretical work and numerous predictions [3,4,5,6,7,8,9,10] make the experimental investigation of large-D spin-1 chains a topical problem in low-dimensional magnetism.Recently, weakly-coupled spin-1 chains have attracted renewed interest due to their possible relevance to the fieldinduced Bose-Einstein condensation (BEC) of magnons. When the field H, applied perpendicular to the easy plane, exceeds a critical value H c1 (defined at T = 0), the gap closes and the system undergoes a transition into an XY -like AFM phase with a finite magnetization and AFM magnon excitations.…”

“…While the underlying physics of Haldane chains is fairly well understood, relatively little is known about the magnetic properties (and particularly the elementary excitation spectrum) of nonHaldane S = 1 AFM chains in the large-D phase. Intense theoretical work and numerous predictions [3,4,5,6,7,8,9,10] make the experimental investigation of large-D spin-1 chains a topical problem in low-dimensional magnetism.…”