DC AND AC MAGNETIZATION AND SMALL-ANGLE NEUTRON-SCATTERING STUDIES OFSTRONGLY INTERACTING PARTICLE-SYSTEMS

MnZn-ferrite particles were randomly dispersed in polymer matrix in wh ich the magnetic anisotropy axes in the particles are randomly oriente d. DC and AC magnetization and small-angle neutron scattering measurem ents have been made on the samples. The DC and AC susceptibilities sho wed spin-glass-like maxima at temperatures that depend on the interpar ticle interaction. The thermal evolution of remanence I-r and coercivi ty H-c was also considerably dependent on the interparticle interactio n, i.e., the temperature at which I-r and H-c tend to zero increased w ith increasing the interparticle interaction energy. This suggests tha t a magnetic correlation occurs through the interparticle interaction in the present sample. The temperature dependence of imaginary part of the AC susceptibility chi '' showed a singular cusp at a low temperat ure which is insensitive to the interparticle interaction. This singul arity in chi '' could reflect a blocking phenomena which is attributed to the intraparticle anisotropy. The small-angle magnetic neutron sca ttering line shape over a temperature range of 6 less than or equal to T less than or equal to 260 K could be represented by a function of L orentzian plus squared Lorentzian which is appropriate for a random an isotropy held system. The data did not show a divergence in the magnet ic correlation length, but suggested the formation of a local ferromag netic cluster composed of the magnetic moments of the adjacent particl es below 260 K. The correlation length increases with decreasing tempe rature. Around 40 K, it shows a maximum and starts to decrease with de creasing temperature. This decrease in the correlation length with dec reasing temperature could arise from the random field effect which cou ld originate from the intraparticle anisotropy. (C) 1998 Elsevier Scie nce B.V. All rights reserved.