Formation of magnetic phases in rapidly quenched Mn-Based systems

Abstract

This work presents the investigation of joint effects of the alloying of constituent elements (in ratio about 1/1) in binary Mn-Al and Mn-Bi together with the process of rapid quenching on the changes of physical properties caused by structural transformations. In order to achieve high magnetic anisotropy the ribbons produced by melt-spinning method were annealed using diverse regimes to obtain the required phase composition and structure. It was shown that the annealing regime has a direct influence on the relevant magnetic properties – remanent magnetization, coercivity and Curie temperature.The content of hard magnetic phases determines the suitability of each material to be used as a permanent magnet. In Mn-based alloys this property results from the existence of specific phases: τ-MnAl in Mn-Al, and low-temperature phase (α-MnBi) in Mn-Bi. The structure evolution and phase transformations from as-cast state was analyzed by calorimetric and thermogravimetric measurements. The formation and evolution of magnetic crystalline phases was monitored by structure analysis using transmission electron microscopy and X-ray diffraction. The results of in-situ phase analyses by exposure to a defined thermal regime was also presented and correlated with the formation of the magnetic phases.