EffectsofFedopingonacsusceptibilityofPr0.75Na0.25MnO3

<正>Ac susceptibility at low temperatures of Pr0.75Na0.25Mn1-xFexO3（0≤x≤0.30） is investigated.The peak value of the real component of ac susceptibility x' at the freezing temperature Tf is suppressed with the increasing frequency. The peak value of x' shows a linear relation between Tf and the logarithm of the frequencyω.The normalized slope P =△T_f/T_f△lgω,which is much lower than canonical insulating spin glass systems in which 0.06≤P≤0.08.The peak value of the imaginary component of the ac susceptibility x" at T_f for the x = 0,0.02,0.30 samples increases with increasing frequency,suggesting a cluster glass ground state with a coexistence of charge-ordered phase and correlated ferromagnetic clusters in spin glass matrix.The peak value of x" at T_f for the x = 0.10 sample decreases with increasing frequency,suggesting a phase separation ground state.The peak value of x" at T_f for the x = 0.05 sample decreases with increasing frequency forω≤52 Hz and increases subsequently till 701 Hz,and then decreases with further increasing frequency forω≤1501 Hz.This complex behaviour is ascribed to the competition between the effects of large and little ferromagnetic clusters in the sample.The ground state of x = 0.05 sample is a transition state from cluster glass to phase separation.