Identification of a Griffiths-like phase and its evolution in the substituted pyrochlore iridates Y2Ir2-xCrxO7 (x=0.0, 0.05, 0.1, 0.2)

We report the Griffiths phase (GP)-like state along with a cluster-glass-like state in geometrically frustrated antiferromagnetic Cr-substituted Y2Ir2O7 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 Cr3+ divided by(sic) Cr3+, Ir4+ divided by(sic) Ir4+, Ir4+ divided by(sic) Cr3+, and Ir4+ divided by(sic) Ir5+ leads to the competition between antiferromagnetic and ferromagnetic correlations. It gives rise to Ruderman-Kittel-Kasuya-Yosida (RKKY)-like interaction between Cr3+ local magnetic moments mediated by itinerant Ir conduction electrons, hence, as a result, GP and cluster-glass-like states emerge.