Identification of a Griffiths singularity in a geometrically frustrated antiferromagnet

Abstract

We report the observation of a Griffiths phase in the geometrically frustrated antiferromagnet DyBaCo 4 O 7 + δ . Its onset is identified using measurements of the thermoremanent magnetization, which appears to be superior to conventional in-field measurement protocols for the characterization of the Griffiths phase. Within this phase, the temporal relaxation of magnetization exhibits a functional form which is expected for Heisenberg systems, reflecting the nature of spin interactions in this class of materials. Interestingly, the effective Co 2 + / Co 3 + ratio tailored by varying the oxygen nonstoichiometry δ is only seen to influence the antiferromagnetic ordering temperature ( T N ), leaving the Griffiths temperature ( T G ) invariant.