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In this work , we report the self - assembly of binary nanocrystal superlattices composed of magnetically hard CoFe 2 O 4 nanocrystals and magnetically soft Fe 3 O 4 nanocrystals .
 Chemical: CoFe 2 O 4; Chemical: Fe 3 O 4
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: CoFe 2 O 4; Chemical: Fe 3 O 4