Magnetism in Granular Systems

Abstract

Previous experimental studies have shown that the magnetic dipolar interaction plays an important role in several magnetic properties of nanoparticulated systems. More recently, this type of interaction was detected in microparticles of Fe-Mn-Al, Fe-Si and Fe-Al systems. In this work, we apply the Mørup-Tronc (Phys. Rev. Lett. 72:3278, 1994) model for nanoparticulated systems in order to calculate some thermodynamic properties of these systems. We first calculated the total energy of a magnetic particle as the sum of its anisotropy energy and its total dipolar magnetic interaction with the other particles. The calculation is performed in such a way that the interaction energy has the same form as the anisotropy energy. We use the total energy to calculate the magnetization, heat capacity, magnetic susceptibility, and blocking temperature in nanoparticulated systems. The application of our theory to experimental data on nanoparticulated systems and for the Fe-Al, Fe-Si and Fe-Mn-Al microparticulated granular systems will be presented elsewhere.

Magnetism in Granular Systems II

“…Considering the result previously obtained with our model for the magnetization [1], the partial derivative of the free energy is given by the expression…”

“…In the previous study [1], we obtained the expression for the blocking temperature, T B , assuming a system of singledomain, uniaxial particles with volume V 0 , and interacting via an average dipolar magnetic field < B i >. The expression obtained is given by the following:…”

“…Nanomagnetic particles are very M. Salazar manuels 1965@yahoo.com 1 Pitt Community College, P.O. Drawer 7007, Greenville, NC 27835-7007, USA important for their wide range of applications, including their use to obtain hard or soft magnetic materials, magnetic microsensors, magnetic materials for recording, pigments for paints and ceramics, and in medical and pharmaceutical applications, among others [2][3][4][5][6].…”

“…In our previous study [1], we modified the model of Mϕrup-Tronc [14] for nanoparticulated systems with the objective of obtaining some of their thermodynamic properties. In this model we first calculated the energy of a magnetic particle as the sum of its anisotropy energy and its total energy due to the magnetic dipolar interaction with other particles.…”

“…In this model we first calculated the energy of a magnetic particle as the sum of its anisotropy energy and its total energy due to the magnetic dipolar interaction with other particles. Using a mathematical manipulation, the interacting energy proposed by [1] was modified to write it in the same form as the anisotropy energy and to calculate the magnetization and magnetic susceptibility. In the present study we calculate analytically the coercive field and the heat capacity and show their graphic dependence with respect to temperature.…”