Zeeman splitting of the 63,65Cu NQR line in optimally doped Hg1Ba2Ca2Cu3O8+δ below Tc

We report pure zero field nuclear magnetic resonance (NQR) measurements on the optimally doped three layer compound Hg1Ba2Ca2Cu3O8+δ (Hg-1223) with Tc=134 K. Above Tc two Cu line pairs are observed in the spectrum corresponding to the two inequivalent Cu lattice sites. Below Tc the Cu NQR spectrum shows a splitting of these two line pairs into six line pairs. From a multiexponential spin lattice relaxation with a dependency on the initial conditions, we find a formation of magnetic moments in the CuO layers as the origin of the line splitting. Furthermore, the magnetic moments are oriented parallel to the symmetry axis of the electrical field gradient tensor with magnitudes of the order of 1000 G