We study the spin fluctuation of the oxygen deficient planes of YBa2Cu3O6+x. The Cu-O chains that constitute these planes are described by a model that includes antiferromagnetic interactions between spins and Kondo-like scattering of oxygen holes. The spectrum of magnetic excitations shows the presence of incommensurate dynamic fluctuations along the direction of the chains. The presence of it...

Although the low-frequency electronic Raman response in the superconducting state of the cuprates can be largely understood in terms of a d-wave energy gap, a long-standing problem has been an explanation for the spectra observed in the A1g polarization orientations. We present calculations which suggest that the peak position of the observed A1g spectra is due to a collective spin fluctuation ...

Manuscript is plain TeX with macros. Figures start at FIGURES BEGIN HERE, with instructions on what to do to get them. In this paper, a generalization of standard spin fluctuation theory is considered by replacing the simple Hubbard interaction by the screened Hartree-Fock interaction for f electrons. This model is then used in both an LS and a JJ coupling scheme to construct the particle-parti...

Interacting multi-component spin systems are ubiquitous in nature and in the laboratory. As such, investigations of inter-species spin interactions are of vital importance. Traditionally, they are studied by experimental methods that are necessarily perturbative: e.g., by intentionally polarizing or depolarizing one spin species while detecting the response of the other(s). Here, we describe an...

Spin structure and phase transition of mixtures with competing anisotropies are investigated by a theory which takes static fluctuation of thermal averages of spins into consideration. It is found that random off-diagonal interaction between neighboring spins induces orientational distribution of spins and affect the second order phase transition. Random mixtures of two kinds of spins with orth...