Magnetic field effect on the dielectric constant of glasses: Evidence of   disorder within tunneling barriers
  The magnetic field dependence of the low frequency dielectric constant $e_r$(H) of a structural glass a - SiO2 + xCyHz was studied from 400 mK to 50 mK and for H up to 3T. Measurement of both the real and the imaginary parts of $e_r$ is used to eliminate the difficult question of keeping constant the temperature of the sample while increasing H: a non-zero $e_r$(H) dependence is reported in the same range as that one very recently reported on multicomponent glasses. In addition to the recently proposed explanation based on interactions, the reported $e_r$(H) is interpreted quantitatively as a consequence of the disorder lying within the nanometric barriers of the elementary tunneling systems of the glass. 
J. Le Cochec (CEA/Saclay, Drecam/LPS, France), F. Ladieu (CEA/Saclay,   Drecam/LPS, France), P. Pari (CEA/Saclay, Drecam/Spe...