2519
The effect of varying the surfactant and solvent medium on the dynamics of spin - lattice relaxation in photoexcited Fe3O4 nanocrystals has been investigated by measuring the time - dependent magnetization employing pump - probe transient Faraday rotation technique .
 Chemical: Fe3O4
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: Fe3O4