REVERSIBLE MECHANISM OF MAGNETOTHERMAL INSTABILITIES IN MELT-TEXTUREDYBACUO

The anisotropy of the development of instabilities in the melt-texture d YBaCuO samples with remanent magnetization of 600 emu/g has been stu died in a magnetic field up to 12 T. Large 500 emu/g jumps of the magn etic moment of the sample due to the development of the magnetothermal instability have been observed. A giant (10(-4)) magnetostriction cau sed by the magnetic flux pinning has been revealed. Stabilization of t he critical state of the sample by reversal of magnetization has been found. However, when the sample is heated to temperatures higher than 100 K and subsequently cooled the magnetic jumps restore completely. A new reversible mechanism of instability generation based on the pheno menon reversibility of plastic deformations of high-temperature superc onductors (HTS) is proposed to explain the regeneration of critical st ate instability.