Relaxation phenomena in super spin glass nanoparticle manganite La0.7Ca0.3MnO3

► Magnetic relaxation in super spin glass nanoparticle La0.7Ca0.3MnO3 obtained by mechanochemistry. ► Thermoremanent and zero-field cooled magnetization time dependence, and ageing effect. ► Successful modelling of data by implementation of nonequilibrium spin glass dynamics. ► Glassy behaviour is the consequence of random orientation of easy axes and dipolar interactions between nanoparticles. ► Analysis of spin dynamics during the system ageing.