Magnetization dynamics in rare earth Gd3+ doped Mn0.5Zn0.5Fe2O4 magnetic fluid: Electron spin resonance study

► Zero field cooled spectra exhibit an isotropic resonance field shifts below 50 K. ► Field cooled spectra show angle dependent hysteresis below 50 K. ► Results point to the presence of surface spin glass structure at low temperature. ► Dc-susceptibility results show the presence of two different energy barriers.