Cluster glass transition in [formula omitted

Abstract

We performed linear and nonlinear AC magnetic susceptibility measurements on Ca 2 - x La x MnO 4 ( x = 0.03 , 0.07 , 0.10 , and 0.14). In such manganites, coexistence or competition brings about various phenomena. We focus on a cluster glass state consisting of ferromagnetic clusters within an antiferromagnetic matrix because the coexistence of the ferromagnetic double exchange interaction and the antiferromagnetic superexchange interaction is closely associated with phase separation. As a result, temperature ( T ) dependence of a linear susceptibility ( X 0 ′ ( T ) ) exhibits a sharp peak for x = 0.03 , and these peaks become broad with increasing x . The X 0 ′ ( T ) curves for x = 0.07 and 0.10 show a typical frequency dependence around the peaks, suggesting a cluster (spin) glass transition. Furthermore, a nonlinear susceptibility ( X 2 ′ ( T ) ) for x = 0.10 exhibits successive transitions: the ferromagnetic transition in each cluster occurs at ∼ 108 K and the antiferromagnetic transition between the ferromagnetic clusters occurs at ∼ 89 K . From the X 0 ′ ( T ) and X 2 ′ ( T ) curves for various values of x , we found the existence of the ferromagnetic clusters within the antiferromagnetic matrix, and the cluster glass state was realized for 0.07 ⩽ x ⩽ 0.14 .