Measurement and understanding of magnetization in AC and DC fields and the determination of intragrain H<inf>c1</inf> in high T<inf>c</inf> RBa<inf>2</inf>Cu<inf>3</inf>O<inf>7</inf> superconductors

We present DC and low frequency AC magnetization measurements on various RBa2Cu3O7 superconductors. We identify features intrinsic to these compounds, and establish the features originating from intergranular links in sintered pellets. The isothermal magnetization curves, and the temperature dependence of magnetization in field-cooled and zero field-cooled states are shown to be consistent with the calculations done following a recent extension of Bean’s model. Low field anomalies predicted within this model are observed, and yield Hc1 values of a few Oe. These values are shown to be consistent with the temperature variation of magnetization. A comparison is made with the other existing data and it is demonstrated that earlier quoted values of Hc1 are gross overestimates. © 1988, the Indian Academy of Sciences. All rights reserved.