Mn have been found to be an interesting ion to be used as dopant in Lithium Niobate (LiNbO3) crystals in order to enhance their photorefractive properties. These materials are extremely interesting in order to develop future holographic memories. However, the position of the Mn in the LiNbO3 lattice, and their dependence with the Mn concentration in the crystal has not been studied. In this work we propose to analyse the the position of Mn ions in LiNbO3 crystals, both congruent and stoichiometric by using muSR technique at ISIS. The Crystals will be grown in our Lab at the University Autónoma of Madrid by the Czchralski technique. Several Mn concentrations ranging from 0.5% wt up to 5 % wt will be analyse. Temperatures ranges between RT and 12 K will be used with magnetic fields up to 3500 G