Presentation Information
[P2-15]Study of mechanism to improve the Magnetic Properties of Nd-Fe-B magnets by Dy addition using the Density Functional Theory Calculations
*SHRANTIK KUMAR DEY1, SHAMPA AICH1 (1. IIT KHARAGPUR, Kharagpur, WB, PIN- 721302 (India))
Keywords:
Rare-earth Magnets,Intrinsic Coercivity,Density Functional Theory,Maximum Energy Product,Electric Vehicle applications
New materials and techniques are being used to attain extremely high magnetic fields in permanent magnet-based accelerator magnets that may offer a viable alternative to their conventional electromagnetic counterparts for many applications, especially where strong gradients, low power consumption and less radiation damage are needed [1]. Rare-earth magnets are characterized by high energy product {(BH)max}, high intrinsic coercivity (Hci) and reasonably high remanence (Br). Sm-based and Nd-based magnets are commonly used rare-earth systems. Of these, Sm-based alloys have high temperature stability and high resistance against demagnetization at high temperature, while Nd-based alloys have high remanent field/energy values but poor temperature stability [2]. Material processing techniques often plays a vital role in enhancing magnetic properties of Permanent magnets. Controlling the cooling rate during the material processing (rapid solidification) is very important in order to improve the microstructure and magnetic characteristics of the material. Melt-spinning is the mostly used technique among the numerous rapid solidification procedures since it allows for a high degree of material property control and hence improves the coercivity and remanence of the permanent magnets. The melt-spun ribbon develops Nano-structure as a result of rapid solidification which enhances its properties as compared to the bulk samples. Moreover, the Nd-Fe-B melt spun ribbon forms an in-situ Nano-composite with Alpha-Iron and Nd2Fe14B, with the former being a soft magnetic phase, while the latter being a hard magnetic phase. These hard and soft magnetic phases can be decided based on the Magnetic Moments calculated by the Density Functional Theory calculations. The exchange coupling between the soft and the hard magnetic phases helps in significant increase in the remanence value. In this study the effect of adding Dy as an alloying element to the Nd-Fe-B magnetic system was evaluated by preparing the samples via Rapid Solidification (melt-spinning) process. Micron-thin Ribbons of composition Nd2-xDyxFe14B (x=0 and 0.6) were synthesized, keeping the spinning wheel speed at 30 m/s. Thereafter, the rapidly solidified ribbons were studied by various characterization techniques. X-Ray Diffraction study along with the Rietveld refinement was performed to understand the phase formation behavior and phase fraction quantification. The magnetic properties of different phases present in the ribbons was calculated by DFT calculations. SQUID measurements were done to investigate the magnetic properties of the ribbons. Dy addition increased the maximum energy product [(BH)max] 2-fold, while the coercivity values were observed as 2.4 kOe and 8.1 kOe for Nd2Fe14B and Nd1.4Dy0.6Fe14B ribbons, respectively. Microstructure was observed with the help of Field Emission Scanning Electron Microscope (FESEM). The improved coercivity without compromising remanence was possible because of the intergranular exchange coupling between the soft and the hard magnetic phases.
REFERENCES
[1] Joel, and G.L. Bec. "Prospects for the use of permanent magnets in future accelerator facilities" Proceedings, 5th International Particle Accelerator Conference (IPAC 2014): Dresden, Germany, June 15-20, 2014, TUZB01.
[2] G. Oliver. "High-temperature samarium cobalt permanent magnets" Nanoscale Magnetic Materials and Applications. Springer, Boston, MA, 2009. 337-372.
REFERENCES
[1] Joel, and G.L. Bec. "Prospects for the use of permanent magnets in future accelerator facilities" Proceedings, 5th International Particle Accelerator Conference (IPAC 2014): Dresden, Germany, June 15-20, 2014, TUZB01.
[2] G. Oliver. "High-temperature samarium cobalt permanent magnets" Nanoscale Magnetic Materials and Applications. Springer, Boston, MA, 2009. 337-372.
