Effect of Zn doping in under- and over-doped LaFe1−xCoxAsO system Yuke Li, Chenyi Shen, Yongkang Luo, Xiaojun Yang, Qian Tao, Guang-Han Cao and Zhu-An Xu EPL, 102 3 (2013) 37003 Published online: 15 May 2013 DOI: 10.1209/0295-5075/102/37003