Effect of different element doping on the structure and magnetic properties of composite crystal Sr14(Cu1−xMx)24O41 (M=Zn, Ni, Co)

Abstract The Zn 2+ , Ni 2+ and Co 3+ doped Sr 14 (Cu 1− x M x ) 24 O 41 composite crystals were synthesized by a standard solid state reaction method. The temperature dependence of magnetic properties was measured for every sample. The Curie coefficient, Weiss temperature, number of dimers in CuO 2 chain per formula unit (f.u.) and dimer coupling constant are obtained by fitting the temperature dependence of the magnetic susceptibility. Meantime, selected area electron diffraction patterns (EDPs) show that the diffraction spots corresponding to the CuO 2 chain substructure are extended to streaks along a ⁎ and b ⁎ directions for all the samples, while the diffraction spots produced merely by the Cu 2 O 3 ladder substructure are still very sharp. This means that the periodicities of chains in a ⁎ and b ⁎ directions are partially destroyed upon doping of Zn, Ni and Co due to that the initial phase of each chain becomes a random variable. Considering the effect of different ions substitution for Cu on the magnetic susceptibility, it is found that the degree of initial phase disorder is related to the order degree of magnetic sequence in CuO 2 chain. For the un-doped sample, the decoupling of dimers is weak, the magnetic sequence is slightly destroyed, and the streaks in EDP are also very weak, which implies the degree of initial phase disorder in CuO 2 chain is very low. When Zn 2+ and Ni 2+ ions are doped, the number of dimers per f.u. decreases, and the intensity of diffraction streaks increases. Furthermore, when the high spin magnetic ions Co 3+ are doped, the number of holes in Sr 14 (Cu 1− x Co x ) 24 O 41 decreases, the magnetic sequence is destroyed very seriously, and the spots in EDP are extended to streaks almost completely. The phenomenon that the diffraction spots of CuO 2 chain extend to streaks in EDP appears as evidence that the magnetic sequence in the CuO 2 chain is destroyed by doping of Zn, Ni, Co.