Identification of Griffiths-like phase and its evolution in Cr substituted pyrochlore iridates $Y_2Ir_2O_7$

Abstract

We report the Griffiths phase (GP)-like state along with cluster-glass-like state in geometrically frustrated antiferromagnetic $Cr$ substituted $Y_2Ir_2O_7$ pyrochlore iridates. The strength of GP-like behaviour increases with substitution. Interestingly, isothermal remanent magnetization suggests the Ising-like interaction of spins in GP region. The GP-like state is not attributed to the structural disorder as substitution of Cr does not induces any structural change. Then the spin coupling between $Cr^{3+} \leftrightarrow Cr^{3+}$, $Ir^{4+} \leftrightarrow Ir^{4+}$, $Ir^{4+} \leftrightarrow Cr^{3+}$ and $Ir^{4+} \leftrightarrow Ir^{5+}$ leads the competition between antiferromagnetic and ferromagnetic correlations. It give rise to Ruderman-Kittel-Kasuya-Yosida (RKKY)-like interaction between $Cr^{3+}$ local magnetic moments mediated by itinerant $Ir$ conduction electrons, hence, as a result GP and cluster-glass-like states emerges.