ESR study of doping effects on the spin-Peierls transition in CuGeO3

The effect of doping with nonmagnetic Zn2+ ions on the spin-Peierls transition in pseudo-one-dimensional CuGeO3 has been studied by ESR intensity and electron spin-lattice relaxation time measurements as functions of temperature. The results show that impurity doping in Cu0.97Zn0.03GeO3 reduces the magnetic energy gap much more than the spin Peierls transition temperature. Our results thus provide experimental support for recent theoretical predictions that a gapless spin-Peierls state may take place in Zn+ doped CuGeO3 at intermediate doping levels in analogy to gapless superconductivity.