Raman magnon scattering

Inelastic scattering of radiation in solids is typified by the Raman effect, which involves the creation or annihilation of phonons or magnons. If a single phonon is involved, the scattering event is referred to as the first-order Raman effect in second-order Raman effect two phonons are involved. The polarizability associated with a phonon mode can be represented as a power series of the phonon amplitude, u, as follows ... 

Fig. 12. Raman scattering from magnons in NiF2 in the antiferromagnetic (T < 7 ) and paramagnetic (T> rN) phases S9>. Ndel temperature rN = 73 K. Threefold intensity scale above 88 K...

The use of lasers for the excitation of Raman spectra of solids has led to the detection of many new elementary excitations of crystals and to the observation of nonlinear effects. In this review we have tried to lead the reader to a basic understanding of these elementary excitations or quasi-particles, namely, phonons, polaritons, plasmons, plasmaritons, Landau levels, and magnons. Particular emphasis was placed upon linear and stimulated Raman scattering at polaritons, because the authors are most familiar with this part of the field and because it facilitates understanding of the other quasi-particles. 

Abstract Electronic correlation effects in La2.ISrINi04 lead to spontaneous phase separation into microscopic spin/charge stripes with commensurate or incommensurate order. Raman scattering experiments on such single crystalline materials show a rich phenomenology of phonon and magnon anomalies due to the new, self-organized periodicities. These effects are observable as function of temperature. 

Key words Raman scattering, stripe ordering, phonon and two-magnon excitations... 

Fig. 6. Diagram of the two-magnon Raman scattering process in the cuprates (a) initial antiferromagnetic spin configuration on the Cu sites (b) incident photon excitation of a spin-up Cu(3d ) hole to an intermediate-state 0(2p) orbital (c) double spin flip due to direct spin exchange between the spin-up hole on the intermediate-state 0(2p) site and a spin-down hole on a nearest-neighbor Cu site (d) hopping of a spin-down hole from the 0(2p) intermediate state to the original copper site, emitting the scattered photon.

S Venugopalan, A Petrou, RR Galazka, AK Ramdas, S Rodriguez. Raman-scattering by phonons and magnons in semimagnetic semiconductors—Cdi- Mn Te. Phys Rev B 25 2681-2696, 1982. 

The Raman spectra in La2Cu04 is presented in Figure 7.4(a) below the Neel temperature [30]. The polarization configuration is chosen to be the Big symmetry. A peak structure is observed around 3000 cm with a broad width. This is identified as the two magnon Raman scattering. Consider the antiferromagnetic order of the S = 2 spins in Cu02 plane and focus on a Cu(/)-0-Cu(/) bond where i and j indicate Cu sites. The incident photon excites an electron with up spin from... 

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