Electronic band effects on the spin disorder resistivity of Gd(4)(Co(1-x)Cu(x))(3) compounds

Specific heat of Gd₄Co₃

The specific heat (C(T)) of Gd₄Co₃ was measured in the temperature range 2-300 K and its magnetic contribution (C(m)(T)) was determined using a new method that fits the electronic specific heat coefficient (γ) and the Debye temperature (θ(D)) by constraining the resulting magnetic entropy (S(m)(T)) to saturate at temperatures far above the Curie temperature (T(C)). C(m)(T) exhibits a low-temperature bump originating from thermal excitation of gapped spin waves, which is responsible for pronounced peaks, at ≈35 K, in both C(m)/T and the temperature derivative of the magnetic contribution to electrical resistivity (dρ(m)/dT). Apart from in the vicinity of T(C), an excellent global correlation was found between C(m)/T and dρ(m)/dT. Our results provide strong support for the consistency of the new method proposed for the determination of C(m)(T) and rule out any major role of short-range order on Gd moments or d-electron spin fluctuation effects in the paramagnetic phase. A comparative analysis with other methods used in similar compounds points to the need for a better evaluation of C(m)(T) in such compounds, especially in the magnetically ordered phase, where a deficient evaluation of C(m)/T has a larger impact on the S(m)(T) curve.