Pseudo-gap and the nonlinearity of the magnetization of textured polycrystals of YBa2Cu3O7 − x above the temperature of transition into the superconducting state

Temperature dependences of the third and other higher harmonics of the magnetization of textured polycrystalline samples of YBa2Cu3O7 − x have been studied in the temperature range of 77–120 K. It has been revealed that the nonlinearity of magnetization of YBa2Cu3O7 − x is observed up to temperatures that considerably exceed the temperature of transition into the superconducting state. The observed nonlinearity of magnetization of YBa2Cu3O7 − x is ascribed to the appearance of a pseudogap state at T ∼ 102 K in this compound. A method of determining the temperature of the appearance of the pseudogap T * in the high-T c compounds is suggested, which is based on the measurement of magnetization harmonics.