Structure and magnetic properties of Co-Zn substituted hexagonal ferrites Erfan Handoko, Anggoro B S, Iwan Sugihartono, Mangasi AM, Dini Siti Nurwulan, Serafin Christina and Zulkarnain Jalil MATEC Web Conf., 197 (2018) 02007 Published online: 12 September 2018 DOI: 10.1051/matecconf/201819702007