Static and dynamic response of cluster glass in ${\mathrm{La}}_{0.5}$${\mathrm{Sr}}_{0.5}$${\mathrm{CoO}}_3$

The static and dynamic response of cluster glass in ${\mathrm{La}}_{0.5}$ ${\mathrm{Sr}}_{0.5}$ ${\mathrm{CoO}}_3$ has been experimentally investigated through linear and nonlinear ac susceptibility measurements in the frequency range 137 Hz to 1370 Hz; ac field (1–10 Oe), dc field (0–40 Oe). Field cooled and zero field cooled dc magnetization data have also been reported. An attempt has been made to compare the dynamic response of cluster glass with spin glass, reentrant spin glass, and canted spin systems. The interesting observation is that in the cluster glass system, the coercivity at low fields under the zero field cooled condition does not increase rapidly, as one approaches the so-called freezing temperature (${\mathit{T}}_{\mathit{f}}$), unlike that in typical reentrant spin glass systems. We also observed a linear relation of field cooled coercivity, ${\mathit{H}}_{\mathit{c}}^{\mathrm{FC}}$ (i.e., the coercive force to bring the thermoremanent magnetization to zero) with cooling fields (${\mathit{H}}_{\mathrm{FC}}$) at different temperatures. The variation of ${\mathit{dH}}_{\mathit{c}}^{\mathrm{FC}}$/${\mathit{dH}}_{\mathrm{FC}}$ with T(K) shows an exponential behavior for T⩽${\mathit{T}}_{\mathit{c}}$. We believe that this is a significant observation for cluster glass systems. © 1996 The American Physical Society.