Extra T-linear specific heat contribution induced by the f–d-exchange in Gd–Ni binarycompounds

Abstract

Specific heat measurements performed for Gd–Ni binary compounds with 1:2, 1:1and 3:1 stoichiometry have revealed an additional contribution to the coefficientγ ofthe T-linear term of the low-temperature specific heat in comparison withthat obtained for isostructural paramagnetic counterparts R–Ni(R = Y, Lu, La). Thisextra contribution Δγ is found to grow linearly with increasing Gd concentration from nearly zero forGdNi5 up toΔγ≈21.5 mJ g-at.−1 K−2 forGd3Ni. To explain theappearance of Δγ and its dependence on the strength of the f–d exchange interaction in Gd-rich binary compounds withNi a new mechanism enhancing the effective mass of conduction electrons is suggested. The increasedγ value in Gd-containing compounds is attributed to spin fluctuations induced by the f–dexchange interaction in the hybridized 3d–5d electron subsystem.