Thermal conductivity of pure and Mg-doped CuGeO3 in the incommensurate phase - art. no. 214407

The thermal conductivity kappa of Cu1-xMxGeO3 is measured in magnetic field s up to 16 T. At the transition held H-c to the high-field incommensurate ( I) phase, kappa abruptly decreases. While kappa of the pure CuGeO3 is enhan ced with the application of the higher magnetic held above H-c, such an enh ancement disappears below Neel temperature in Mg-doped samples and kappa (H ) shows an anomalous plateau feature. With the help of specific heat data, taken supplementally for the identical samples, the above features are well understood to show that phonons are strongly scattered by spin solitons an d that kappa in the I phase is governed by their spatial distribution. In p articular, the plateau feature in the doped samples suggests "freezing" of the solitons, in which antiferromagnetism must be playing an essential role .