Magnetization of superparamagnetics in the state of mechanical anisotropy

Author: Simon Chkhaidze
Co-authors: A. Ugulava, Z. Rostomashvili
Keywords: Ferromagnetism, Superparamagnetism, Nanoparticles
Annotation:

The internal energy of magnetic anisotropy for some nanoparticles dominates over the thermal energy even at room temperature. Strong magnetic anisotropy of nanoparticles can significantly affect the process of magnetization of superparamagnetics. However, if the magnetic anisotropy axes of nanoparticles are oriented randomly, they exert no influence on the process of magnetization proceeding according to the classical Langevin theory. If the axes of nanoparticles are polarized (mechanical anisotropy), the magnetization curve differs significantly from that of Langevin. This paper shows that that the magnetization curve of a superparamagnetic in a state of mechanical anisotropy lies between the Langevin and hyperbolic tangent curves and with increasing anisotropy of nanoparticles is gradually moving away from the Langevin shape and approaches that of the hyperbolic tangent. It is also shown that in the case of powder superparamagnetics, the mechanical anisotropy leads to substantial quantitative changes in the Curie law.