Shallow donor levels enhanced ferromagnetism in the In2O3:Co nanocrystal Zhen-Kun Tang, Li-Ming Tang, Dan Wang, Ling-Ling Wang and Ke-Qiu Chen EPL, 97 5 (2012) 57006 Published online: 02 March 2012 DOI: 10.1209/0295-5075/97/57006