[m'taqgakt] properties OF HEUSLER'S ALLOYS 137 



Alloy jSTo. la, the least magnetic, shewed several types of micro- 

 structure, even over the same section, indicating a lack of homogeneous 

 crystallization on cooling. 



Alloys 2, 2a, were fairly unifonn in appearance, occasional patches 

 of a different structure appearing. From the fact that material of two 

 colours was peen on the surface examined, it was evident that this 

 alloy consisted of crystals of one composition embedded in a matrix of 

 another. Small traces of what appeared to be manganese were met 

 with, and were considered fairly well identified by the fact that this 

 metal is dissolved by dilute acetic acid which attacks neither aluminium 

 nor copper. 



Alloys 3, 3a, 3b, were most magnetic, and upon etching gave a 

 characteristic appearance. Distinct areas arranged like tiles in a floor 

 were seen separated by thin layers of a material of another kind. Scat- 

 tered through these areas, or along their edges, were a large number 

 of fern-shaped or tree-like aggregations of what seemed to be manganese. 

 Fig. 4 shews areas with these figures, and Fig. 5 shews one of the fern- 

 shaped figures viewed with a higher power. All the areas presented 

 a homogeneous appearance, the three rods being apparently quite uni- 

 form throughout. 



Alloys 4, and 4a were slightly less magnetic than 3, 3a, and 3b, and 

 shewed a similar microstimcture. The larger areas were separated by 

 thicker layers of material than in the last mentioned, while the fern- 

 shaped figures were modified to smaller rosette or star-shaped aggre- 

 gations. 



As stated a.bove, the highest magnetization was exhibited by- the 

 alloys 3, 3a, 3b, 4, 4a. With these there was found a definite form 

 of crystallization consisting of an aggregation of uniform crystals enclos- 

 ing a special form of what was apparently crystalliTip manganese. 



Since in both alloys 4, 4a, as well as in 3, 3a, 3b, the larger areas 

 seemed to be the same, it would seem reasonable to conclude that the 

 magnetic properties were associated with and accompanied this special 

 form of manganese. This, at least, appears to be a probable conjecture, 

 but additional experimental work is needed before the relation indicated 

 can be considered established. With this purpose in view the investiga- 

 tion is being continued. 



The writer wishes to express in this place, his thanks to Prof. 

 McLennan for his kindness in placing at his disposal the necessary 

 apparatus, and for his many helpful suggestions given from time to 

 time during the investioration. 



