Magnetic properties of Zn-doped Haldane-gap material NENB

Experimental studies of magnetic susceptibility and electron-spin resonance (ESR) properties of the spin-1 Haldane-chain material Ni(C₂H₈N₂)₂NO₂ doped with non-magnetic Zn-ions in a range up to 5% are reported. The presence of fractional S = 1/2 chain-end states, revealed by ESR and susceptibility measurements in nominally pure single crystals of NENB, is found to be responsible for spin-glass freezing effects. Higher doping ratio of Zn-ions suppresses the spin-glass behaviour by creating shorter and isolated chain fragments. The effect of non-magnetic doping on the lineshape of ESR spectra of fractional S = 1/2 chain-end states is discussed.