9399
The magnetism measurements showed that the beta - W nanocrystals have weak ferromagnetic properties at 2 K , which may arise from surface defects and unpaired electrons on the surface of the ultrafine nanocrystals .
 W
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 W