HIGH FIELD MUSR STUDY OF SHORT AND LONG RANGE MAGNETIC CORRELATIONS IN CeNi9GeGa3 AND CeNi9Ga4

The interesting magnetic phase diagram results from competing Kondo and RKKY interactions with magnetic frustration. One interesting system in this context may be CeNi9Ga4 and solid solutions CeNi9Ge4-xGax which crystallize in a tetragonalstructure. CeNi9Ge4 was found to be near a heavy fermion quantum critical point, showing a paramagnetic ground state with a huge Sommerfeld coefficient, exceeding 5.5 J/molK² . The latter appears being stabilized by its quasi-quartet crystal field (CEF) ground state degeneracy. In CeNi9Ge4-xGax we observed a long range magnetic order with a maximum TN ~2.8 K for CeNi9Ge3Ga, while CeNi9Ga4 shows a weak magnetic transition near 0.5K, which change from FM-type to AFM-type in an applied field >=0.5T. We therefore proposed here to investigate these compounds using musr measurements on HiFi to understand the complex nature of the magnetic ordering.