Section III., 1908. [ 13S ] Trans. R. S. C. 



IX. — The Coii'sUtuUon and Properties of Heusler's Alloys, including 

 a Study of their Microstructure. 



By H. A. McTaggart, M.A. 



(Communicated by Professor J. C. McLennan, and read May 26th, 1908.) 



The ferromagnetic alloys discovered by Heusler have, in the hands 

 of various investigators/ been found to exhibit physical properties which 

 suggest a close connection between their magnetic behaviour and their 

 crystalline structure. 



Among other properties, the permeability of these alloys has been 

 investigated and found to be a function of their percentage compositions. 



Again, various kinds of heat treatment have been shewn to alter 

 the permeability of the alloys as well as their magnetic hysteresis. 

 Continued heating at about 110^ C, followed by gradual cooling, has 

 been found to produce a considerable increase in their permeability. 

 Kaising the temperature of the alloys above their transformation point 

 (Ca. 200° C.) and then cooling them slowly, leaves a hysteresis effect, 

 while sudden quenching above that point practically eliminates all mag- 

 netic properties. These, however, are again restored by ageing at 

 110° C, but such restoration is accompanied, as a rule, with very little 

 if any hysteresis effect. 



Further, the character of the magnetostriction phenomena exhibited 

 by these alloys has been observed to change with the history and treat- 

 ment of any specimen. 



Similarly, their electrical resistance and the Hall and other alHed 

 effects which have been studied with them exhibit characteristics which 

 vary with the relative proportions in' which the manganese and copper 

 enter into their composition. 



Inasmuch as the different crystalline phases which have been 

 studied with a number of alloys have been shewn to be largely detennined 

 by their percentage composition and by the treatment to which they 

 have been subjected, it would appear that in view of the facts cited above 



^Verh. d. Deut. Phys. Gesell, 5, 219, 1903; Marburg Schriften, 237, 1904; 

 Ann. d. Phys., 16, 535, 1904; Electrician, June 16, 1905; Phys. Rev., 96, 335, 

 1905; Verb. d. Deut. Phys. G-es., 7, 133, 1905; Proc. Roy. Soc, 76, 271, 1905; 

 Phys. Rev., 23, 498, 1906; Bulletin of Bureau of Standards, Washingrton, 

 Vol. 2, No. 2, p. 297, August, 1906; Verb. d. Deut. Ph-s. Gesell, March, 1907; 

 Phys. Rev., 24, 1907; Verb. d. Deut. Phys. Ges., Jan., 1908. 



