Heat-capacity and magnetic measurements on the Y(${\mathrm{Ni}}_{2\mathrm{-}\mathit{x}}$${\mathrm{Co}}_{\mathit{x}}$)${\mathrm{B}}_2$C system

We have performed field- and temperature-dependent magnetization, resistivity, and heat-capacity measurements on polycrystalline samples of the Y(${\mathrm{Ni}}_{2\mathrm{-}\mathit{x}}$${\mathrm{Co}}_{\mathit{x}}$)${\mathrm{B}}_2$C system with 0.0≤x≤0.4. Values of ${\mathit{T}}_{\mathit{c}}$,${\mathrm{\chi }}_0$,${\mathit{H}}_{\mathit{c}2}$,${\mathrm{\Theta }}_{\mathit{D}}$, λ, and N(${\mathit{E}}_{\mathit{d}}$) were determined for various samples. We observe that ${\mathrm{\Theta }}_{\mathit{D}}$ increases with x, while all the other parameters decrease with x. The ${\mathit{T}}_{\mathit{c}}$ vs x data can be described using the BCS theory and the measured values of N(${\mathit{E}}_{\mathit{f}}$) and ${\mathrm{\Theta }}_{\mathit{D}}$. The results suggest that the decrease in ${\mathit{T}}_{\mathit{c}}$ is due to the decrease in N(${\mathit{E}}_{\mathit{f}}$), in agreement with the results from band structure calculations. © 1996 The American Physical Society.