Determination of Blocking Temperature in Magnetization and Mossbauer Time Scale: A Functional Form Approach

We studied the temperature,dependence of the magnetization in an ensemble of monodomain nanoparticles both with dc magnetometry and Mossbauer spectroscopy. The analytical form of the temperature dependence is given by the complementary cumulative distribution function. This allows to determine the magnetization blocking temperatures of the sample by a fitting procedure. It is possible to calculate the Mossbauer blocking temperature by a single spectrum and the dc magnetization blocking temperature by, two points of the thermoremanent magnetization curve, thus with a large reduction of the experimental work. The method may be used for particles with not too strong interactions, such happens in the Fe28 sample and not for samples with strong interactions as N30; it may be used for interparticle interaction energies up to 2 yJ and not for energies larger than 60 yJ. This method of analysis of the data should be used in the future work concerning the thermoremanent magnetization and Mossbauer spectra of magnetic nanoparticles.