Correlation between the “fishtail” effect in the magnetization and the Schottky contribution in the specific heat of high purity YBA2Cu3O7−δ crystals

The irreversibility of the magnetization and the low temperature specific heat of high purity YBa2Cu3O7−δ crystals are investigated. We find that the heat treatment that suppresses the magnetic “fishtail” effect also suppresses the Schottky component of the heat capacity. Both effects originate from the distribution of oxygen states.