Evolution of ferromagnetic interactions from cluster spin glass state in Co–Ga alloy

• Temperature dependence of DC and AC susceptibility (acs) analysis has been carried out on CoxGa1−x, (x=54–57).
• M–H data above transition suggests presence of spin clusters.
• A detailed analysis of acs data suggests a cluster glass behavior as oppose to SPM state for x=54 and 55.5.
• Memory phenomena using specific cooling protocols also support the spin-glass features in Co55.5Ga44.5 composition.
• Development of ferromagnetic like behavior for x≥57 has been suggested from DC and AC magnetization data.

Low temperature magnetic properties of binary CoxGa100−x (x=54–57) alloy have been investigated. Analysis of frequency dependence of ac susceptibility provided a conclusive evidence for the existence of cluster spin glass like behavior with the freezing temperature ~8, 14 K for x=54, 55.5 respectively. The parameters for conventional ‘slowing down’ of the spin dynamics have been extracted from the acs data, which confirm the presence of glassy phase. The magnitude of Mydosh parameter obtained from the fits is larger than that reported for typical canonical spin glasses and smaller than those for non-interacting ideal superparamagnetic systems but comparable to those of known cluster-glass systems. Memory phenomena using specific cooling protocols also support the spin-glass features in Co55.5Ga44.5 composition. Further the development of ferromagnetic clusters from the cluster spin glass state has been observed in x=57 composition.