Investigation on three internal friction peaks at low temperature in Ni doped YBa2Cu3O7-delta

Internal friction measurements were performed on seven Ni doped YBCO sample s from 100 to 300K. Three peaks are observed in temperature dependence of i nternal friction. One is located at about 220K(P-1), the other two appears near 98K(P-3) and 110K(P-2), respectively. These peaks show different tempe rature and height dependence on Ni doping. It is speculated that P-3 may be related to a magnetic transition, which is affected by the magnetic impuri ties Ni. P-2 and P-3 may be related to the jumps of O atoms in the Cu-O cha ins and the strong interaction between phonons and spin fluctuations, respe ctively.