  We propose a model for 1/f flux noise in superconducting devices (f is
frequency). The noise is generated by the magnetic moments of electrons in
defect states which they occupy for a wide distribution of times before
escaping. A trapped electron occupies one of the two Kramers-degenerate ground
states, between which the transition rate is negligible at low temperature. As
a result, the magnetic moment orientation is locked. Simulations of the noise
produced by randomly oriented defects with a density of 5*10^17 m^-2 yield 1/f
noise magnitudes in good agreement with experiments.
