1910-11.] On Magnetism of Copper-Manganese-Tin Alloys. 99 
effects were not superposed, or when an allowance was made for their 
occurrence, the susceptibility for high fields was lowered almost to its 
original value, and that for low or moderate fields was reduced to a value 
equal to or less than the initial amount. 
Origin of the Magnetic Properties. — The authors have already suggested 
that the magnetic properties of the Heusler alloys of copper-manganese- 
aluminium are to be ascribed to the formation of a series of solid solutions 
of which the binary compound Cu 3 A1 is a constituent. A similar explana- 
tion may hold in the present instance, and it is proposed to discuss these 
hypotheses in a subsequent paper when an examination of the micro- 
structure of polished samples of the alloys has been concluded. The ternary 
system discussed in the present paper is more complex than the 
Cu + Mn + Al system, in so far as it has been shown that the magnetic 
members fall into at least two distinct divisions. It is interesting to note 
in this connection that manganese and tin form two magnetic compounds 
Mn 4 Sn and Mn 2 Sn,* whereas manganese and aluminium give only one 
magnetic compound Mn 3 Al.-|- 
Summary. 
1. Alloys were prepared containing 14, 16, 18, 30, 38, and 48 per cent, 
of tin, and the remainder copper and manganese in the ratio 7 : 3. 
2. Tests were carried out at different temperatures on the materials as 
cast, normalised, annealed, and quenched. 
3. At 15° C. in the normalised condition the six alloys gave I respectively 
equal to 55, 77, 82, 04, 96, and 1, for H = f00. 
4. When cooled to — 190° C. the three alloys poor in tin were much more 
magnetic. 
5. Annealing produced no decided improvement. 
6. The susceptibility diminishes with increase of temperature, and the 
critical temperatures range from 225° to 275° C. 
7. Quenching produces complex changes in the susceptibility. The 
quenched materials have less coercive force and exhibit greater improvement 
on cooling to —190° C. 
8. Reannealing tends to restore the initial susceptibility of the quenched 
material, but has little influence on the coercive force. 
9. The magnetic properties are probably due to the formation of solid 
solutions of certain definite concentrations. 
* R. S. Williams, Zeit.f. anorg. Chem ., lv., 1 (1907). 
t G. Hindricks, Zeit.f. anorg. Chem., lix., 414 (1908). 
(Issued separately December 22, 1910.) 
