Specific heat of delafossite oxideCuCr1−xMgxO2(0≤x≤0.03)

Abstract

Specific heat, magnetization, resistivity, and structure of delafossite oxide ${\text{CuCr}}_{1\ensuremath{-}x}{A}_{x}{\text{O}}_{2}$ $(A={\text{Mg}}^{2+},{\text{Ca}}^{2+},{\text{Al}}^{3+})$ have been investigated. With the substitution of nonmagnetic ${\text{Mg}}^{2+}$ for ${\text{Cr}}^{3+}$ $(S=3/2)$, the peak of specific heat upon antiferromagnetic (AF) transition becomes sharper and the transition temperature increases. The peak is much affected by a magnetic field of 9 T when ${\text{Cr}}^{3+}$ is substituted by ${\text{Mg}}^{2+}$. Comparing the substitution effect of ${\text{Mg}}^{2+}$ to those of other nonmagnetic ${\text{Ca}}^{2+}$ and ${\text{Al}}^{3+}$, magnetization around the AF transition does not seem to correlate with randomness and lattice parameter but with itinerancy of the doped holes. These results suggest that the residual magnetic frustration stemming from a modulated triangular $120\ifmmode^\circ\else\textdegree\fi{}$ spin structure is partially broken by spin fluctuations, which are enhanced through the interaction between the hole introduced by Mg doping and the localized spin at the Cr site.