Magnetic properties and thermal stabilities of Ga substituted Nd-Fe-Co-B magnets

Abstract

The substitution effect of 20 kinds of elements has been studied in order to increase the intrinsic coercive force for the Nd-Fe-Co-B alloys. The substitution of Ga is found to increase the coercivity more than any other elements. The compositions which are suitable for both magnetic properties and thermal stabilities have been examined. The Ga substitution is compared with the Al and Dy substitutions whose elements are well-known for increasing coercivity. The Ga substitution shows better magnetic properties and lower irreversible losses than the Al and Dy substitutions for the Nd(Fe <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.72</inf> Co <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.2</inf> B <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.08</inf> )5.6 alloy. The magnetic properties and composition which achieve less than 5 % irreversible loss after exposure at 140°C and the permeance coefficient of -2 are as follows; 4πIr = 12.2 kG, <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</inf> H <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</inf> = 16.5 kOe, <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">(BH)_{\max} = 35.2M</tex> MGOe and Nd(Fe <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.7</inf> Co <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.2</inf> B <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.08</inf> Ga <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.02</inf> )5.6.