We aim at performing temperature (2-300K) and magnetic field (0-5T) dependent muon SR on a 1X1 cm2 mosaic, made of 4* 5x5x2 mm3 TbMn0.98Fe0.02O3 single crystals (largest area perpendicular to a-axis) in the HiFi beamline. The main objetives of this experiment are: 1) obtain a local perspective of the ongoing magnetic interactions and distortions due to the effect of Fe3+; 2) characterization of the spin dynamics and fluctuations, as well as, the distribution of local magnetic field, which depends on the commensurability or incommensurability of the spin structure. By joining the muon SR results with those already obtained from neutron diffraction, we expect to disentangle the complexity and origins of the local magnetic fields, disorder and fluctuations due to Fe3+ doping and applied magnetic field, and the disappearance of the electric polarization with increasing magnetic field.