Abstract
Systematic investigation was made on the magnetic property of a series of Nd2Fe14B/α-Fe nanocomposites prepared by crystallization of amorphous Nd8Fe84Ti2B6 ribbon at annealing temperatures in the range of 800-860 °C. Both remanence and energy product increase with increasing annealing temperature, reaching the maximum values at 850 °C. Coercivity remains around 5.5 kOe for the annealing temperatures above 800 °C. Although the smooth demagnetization curve indicates effective exchange coupling between the Nd2Fe14B/α-Fe dual phases, FORC diagram reveals the existence of α-Fe for the Nd8Fe84Ti2B6 ribbon annealed at 850 °C. In addition, the variation of microcoercivity at different locations indicates a distributed exchange interaction, which can be caused by the nonuniform microstructure. The magnetic property is also affected by the demagnetization effect caused by the particle shape, which is evidenced by the negative region in the first-order reversal curve (FORC) diagram.
Highlights
Since the theoretical model for nanocomposite magnet was put forward by Coehoorn et al.1, much work has been done in regards to this topic
The magnetic performance of Nd8Fe84Ti2B6 is significantly affected by annealing temperature, and an optimum combination of magnetic properties is obtained with an annealing temperature of 850 °C
From first-order reversal curve (FORC) diagram we find that the exchange interaction intensity is distributed across a wide range, which results in a wide range of microcoercivity
Summary
Since the theoretical model for nanocomposite magnet was put forward by Coehoorn et al., much work has been done in regards to this topic. Uniform phase distribution in combination with fine grain sizes is needed for excellent magnetic performance in Nd2Fe14B /α-Fe composite. Distributed and refined microstructure can be achieved through crystallization of the amphormos matrix produced by quenching. Distributed and refined microstructure can be achieved through crystallization of the amphormos matrix produced by quenching5,6 Based on this concept, a substantial amount of work has been done to optimize the nanocomposite microstructure. A substantial amount of work has been done to optimize the nanocomposite microstructure Element doping, such as Zr[7], Nb[8], Ti[9], W[10] etc., or combined addition, promotes the formation of amorphous phase by increasing the whole entropy, which may effectively refine the grain size by forming grain boundaries. It is necessary to investigate the crystallization process as well as the corresponding exchange interaction behavior in order to gain a comprehensive understanding and improvement of the magnetic performance
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