  Nuclear magnetic resonance detection in ultra low field regime enables the
measurement of different components of a spurious remanence in the polymeric
material constituting the sample container. A differential atomic magnetometer
detects simultaneously the static field generated by the container and the
time-dependent signal from the precessing nuclei. The nuclear precession
responds with frequency shifts and decay rate variations to the container
magnetization. Two components of the latter act independently on the atomic
sensor and on the nuclear sample. A model of the measured signal allows a
detailed interpretation, on the basis of the interaction geometry.
