Evidence of partial gap opening and Ce-site dilution effects in a heavy fermion compound CeNiGe2

We report the results of magnetisation, non-linear dc susceptibility, electrical transport, and heat capacity measurements on Y-substituted heavy fermion CeNiGe₂. Investigations are carried out on the compounds CeNiGe₂, Ce_0.9Y_0.1NiGe₂, Ce_0.8Y_0.2NiGe₂ and Ce_0.6Y_0.4NiGe₂. It is observed that with the increase in Y-concentration, the magnetic ordering temperature decreases. For CeNiGe₂, below ordering temperature Arrott plots suggest the presence of spin density wave (SDW). Third- and fifth-order dc susceptibility indicates magnetic instability which possibly leads to partial gap opening resulting in the observation of SDW. These observations are further investigated through resistivity and heat capacity measurements which also point toward partial gap opening in CeNiGe₂. Interestingly, with the increase in Y-substitution, it is noted that the gap opening is suppressed and also shifted towards lower temperature. Moreover, our investigations reveal absence of non-Fermi liquid behaviour or zero field quantum critical point even after 40% dilution of Ce-site.