Identification of a Griffiths-like phase and its evolution in the substituted pyrochlore iridates Y2Ir2−xCrxO7

We report the Griffiths phase (GP)-like state along with a cluster-glass-like state in geometrically frustrated antiferromagnetic Cr-substituted ${\text{Y}}_{2}{\text{Ir}}_{2}{\text{O}}_{7}$ pyrochlore iridates. The strength of the GP-like behavior increases with substitution. Interestingly, isothermal remanent magnetization suggests the Ising-like interaction of spins in the GP region. The GP-like state is not attributed to the structural disorder as substitution of Cr does not induce any structural change. Then the spin coupling between ${\text{Cr}}^{3+}\ensuremath{\leftrightarrow}{\text{Cr}}^{3+}$, ${\text{Ir}}^{4+}\ensuremath{\leftrightarrow}{\text{Ir}}^{4+}$, ${\text{Ir}}^{4+}\ensuremath{\leftrightarrow}{\text{Cr}}^{3+}$, and ${\text{Ir}}^{4+}\ensuremath{\leftrightarrow}{\text{Ir}}^{5+}$ leads to the competition between antiferromagnetic and ferromagnetic correlations. It gives rise to Ruderman-Kittel-Kasuya-Yosida (RKKY)-like interaction between ${\text{Cr}}^{3+}$ local magnetic moments mediated by itinerant Ir conduction electrons, hence, as a result, GP and cluster-glass-like states emerge.