In order to optimize the magnetic properties of diehyphen;upset Prhyphen;Fehyphen;B magnets, we have systematically altered alloy compositions, including partial substitution of cobalt and neodymium, and lowhyphen;level additions of gallium. In general, the remanences of Prhyphen;Fehyphen;B diehyphen;upset magnets were lower by sim;1 kG, and coercivities were higher by sim;4 kOe, than analogous Ndhyphen;Fehyphen;B magnets. The microstructure of the Prhyphen;Fehyphen;B diehyphen;upset magnets was similar to Ndhyphen;Fehyphen;B magnets. Both systems are two phase, consisting of oriented flat platelethyphen;shaped grains of 2hyphen;14hyphen;1 separated by a rare earthhyphen;rich intergranular phase. The intergranular phase is thicker for the Prhyphen;Fehyphen;B magnets, resulting in enhanced magnetic domain wall pinning and increased coercivity. Even higher coercivities were obtained with small amounts of cobalt substitution (le;5 at.thinsp;percnt; of the transition metal) and by very lowhyphen;level additions of gallium (le;0.5 at.thinsp;percnt;). The largest remanence (Br=13.7 kG) for a Prhyphen;based 75percnt; diehyphen;upset magnet was obtained with the alloy (R13TM81B6)0.9975Ga0.25, where R=(Pr0.8Nd0.2) and TM=(Fe0.95Co0.05).
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