Studies of Substituted R 2 T 14 B and R 2 Co 17 Systems (T = Fe or Co)
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STUDIES OF SUBSTITUTED R 2 TI 4 B AND R2 Co 1 7 SYSTEMS (T = Fe or Co)
W. E. WALLACE, A. T. PEDZIWIATR, E. B. BOLTICH, H. KEVIN SMITH, S. S. G. SANKAR AND E. OSWALD Mellon Institute and Magnetics Technology Center, Carnegie-Mellon University, Pittsburgh, PA 15213
Y. JIANG,
ABSTRACT Certain R 2 Co 1 7 and R2 T1 4 B systems (R = a rare earth, T = Fe or Co) are of significance for use in the fabrication of high energy magnets. Improvements in these systems as high energy magnet materials are effected by parA description tially replacing Co or T by appropriate d transition metals. is given of the magnetic behavior of a number of systems based on R 2 Co 1 7 and R 2 T 1 4 B. Also, an account is given of recent work dealing with the systems RCo 4 B and PrCo4_xFexB. The latter materials have large magnetizations and high Curie temperatures. However, they are not useful permanent magnet materials because they exhibit planar anisotropy. Results of some Auger spectroscopy studies of R2 Fel 4 B systems (R = Pr,Nd or Er) are presented. This work shows the intergranular region to be rich in B, 0 and R. This region is undoubtedly non-magnetic, a feature which is most probably of significance in regard to the observed coercivity of R 2 Fel 4 B magnets.
INTRODUCTION The subject matter of this paper is divided into 4 parts: (1) the magnetic behavior of Nd2 Fel4B-based alloys, (2) the magnetic behavior of some R2 Co 7 -based alloys, (3) the magnetic behavior of RCo 4 B and PrCo4_xFexB alloys and (4) a preliminary study of the surface features of R2 FeI 4 B systems by Auger spectroscopy. Nd2 FeI 4 B is now recognized as an important material for fabricating high energy permanent magnets. It is well known that its utility is limited by its low Curie temperature, % 315*C. A number of alloy studies have been carried out in the author's laboratory and elsewhere to improve the performance of Nd2 FeI 4 B magnets at elevated temperatures. Some of this work is described in the present paper. A description is also given of the magnetic behavior of alloys based on R 2 Co 1 7 . Some of these systems are of potential significance as permanent magnet materials, except for their unfavorable anisotropies. Favorable anisotropy can be achieved in some instances if the Co is replaced by Fe or Mn or a combination of these. Alloys of composition RCo4_xFexB have been studied because of their general similarity to the important R2 FeI 4 B magnetic phases and their potential as high energy magnet materials. Auger studies have been carried out on a number of R2 Fel 4 B systems to obtain information as to the chemistry of the boundary phases in sintered magnets made from these materials, hopefully leading to an improved understanding of the mechanism of coercivity in these materials.
R 2 Fe 1 4i-
AND R 2 Co 1 4 B-BASED ALLOY SYSTEMS
Many studies have been carried out recently in which substitutions have been made on the various sublattices in R 2 Fel 4 B and R2 Co 1 4 B systems. These can be grouped into three categories as follows:
Mat. Res. Soc. Sym
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