Substituted strontium ferrite SrFe_(12-x)Cr_(x/2)Al_(x/2)O_(19) (x=0-2.5) was prepared by sol-gel method. Ac susceptometer, and ~(57)Fe Mossbauer spectroscopy were used to analyze the structure, static and dynamic magnetic properties of the prepared samples. Mossbauer spectra show that Al-Cr ions preferentially occupy the 12k sites. Magnetic dynamics of the samples was studied by the measurement of ac magnetic susceptibility versus temperature at different frequencies and dc magnetic fields. A frequency-dependent peak was observed in ac magnetic susceptibility versus temperature, which is well described by Vogel-Fulcher model. It was observed that with increasing substitutions, blocking temperature is decreased.
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