Anomalies in the Temperature Dependence of the Local Magnetization in YBa2Cu3O7−δand Nd1.85Ce0.15CuO4−δCrystals

Local magnetic measurements as a function of temperature (mH(T)) in Nd1.85Ce0.15CuO4−d(NCCO) and untwinned YBa2Cu3O7−δ (YBCO) crystals reveal an abrupt increase in the local magnetization at a field dependent temperature, in a certain field range. Both crystals also exhibit a pronounced kink in their local magnetization vs field (mT(H)) curves. However, while in YBCO the anomalies in mT(H) and mH(T) curves occur along the same line in the field-temperature plane, in NCCO the(B,T) locations of the anomalies do not coincide. In both crystals the anomalies in mT(H) are identified as signifying vortex solid-solid disorder induced transition. However, we show that the anomalies in mH(T), although associated with the vortex solid-solid transition, do not necessarily indicate the location of the transition.