The microstructure, high performance magnetic hardness and magnetic after-effect of an alpha- FeCo/Pr(2)Fe(14)B nanocomposite magnet with low Pr concentration.
In this paper, a systematic investigation of the microstructure, high performance magnetic hardness as well as novel magnetic memory effect of the Pr(4)Fe(76)Co(10)B(6)Nb(3)Cu(1) nanocomposite magnet fabricated by conventional melt-spinning followed by annealing at temperatures ranging from 600 to 700 degrees C in Ar gas for nanocrystallization are presented and discussed. Transmission electron microscopy (TEM) observation confirms an ultrafine structure of bcc-Fe(Co) as a magnetically soft phase and Pr(2)Fe(14)B as a hard magnetic phase with a spring-exchange coupling in order to form the nanocomposite state. Electron diffraction analysis also indicates that the Co atoms together with Fe atoms form the Fe(70)Co(30) phase with a very high magnetic moment (2.5 mu(B)), leading to a high saturation magnetization of the system. High magnetic hardness is obtained in the optimally heat-treated specimen with coercivity H(c) = 3.8 kOe, remanence B(r) = 12.0 kG, M(r)/M(s) = 0.81 and maximum energy product (BH)(max) = 17.8 MG Oe, which is about a 25% improvement in comparison with recent results for similar compositions. High remanence and reduced remanence are the key factors in obtaining the high performance with low rare-earth concentration (only 4 at.%). High-resolution TEM analysis shows that there is a small amount of residual amorphous phase in the grain boundary, which plays a role of interphase to improve the exchange coupling. Otherwise, in terms of magnetic after-effect measurement, a magnetic memory effect was observed for the first time in an exchange-coupled hard magnet.
Department of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ, UK. Center for Materials Science, College of Science, Vietnam National University Hanoi, 334 Nguyen Trai, Hanoi, Vietnam.
Duc-The
DT
Ngo
Hong-Gam
HG
Duong
Hoang-Hai
HH
Nguyen
Chau
C
Nguyen
Mohammed
M
Basith
Duc-Quang
DQ
Hoang