Onset of magnetism in Y_1-xGd_xCo₂: Effect on the heat capacity and electrical resistivity

Results of the electrical resistivity, magnetoresistance and specific heat measurements are presented for Y_1-xGd_xCo₂ in the vicinity of the critical Gd concentration x_c ≈ 0.15 for the onset of a long-range magnetic order. Pronounced maxima of the coefficient y of the T-linear specific heat, Debye temperature and residual resistivity as a function of concentration are found to exist at x = 0.1, i.e. just below x _c. These anomalies, together with the existence of a minimum on the temperature dependences of the electrical resistivity at 0 < x < 0.15, are ascribed to the substantial influence of localized spin density fluctuations induced by f-d exchange in the itinerant d-electron subsystem of Co. The maximal extra contribution to the residual resistivity Δρ _res^max in Y_1-xR_xCo₂ pseudobinaries is found to depend on the critical concentration as well as on the type of R ions, while the value of Δγ_max depends only on the critical concentration of R ions. The significant upturns on C _p/T versus T² dependences observed in Y _1-xGd_xCo₂ at 0 < x < 0.15 may be indicative of a non-Fermi-liquid behaviour of the d-electron subsystem caused by the partial substitution of Gd for Y.