^aDepartment of Physics, Government College University Faisalabad, Pakistan bInstitute of Physics, The Islamia University of Bahawalpur

^cDepartment of Physics, Balochistan University of Information Technology,

Engineering & Management Sciences, Quetta 87300, Pakistan

^dDepartment of Chemistry, National Taiwan University, No. 1, Section 4,

Roosevelt Road, Taipei 10617, Taiwan

^eDepartment of Physics and Astronomy, College of Science, P.O. BOX 2455, King Saud University, Riyadh, 11451, Saudi Arabia

^fDepartment of Mechanical & Energy Systems Engineering, Faculty of

Engineering and Informatics, University of Bradford, Bradford BD7 1DP, United Kingdom

^gDepartment of Physics, University of Central Punjab, Bahawalpur Campus,

Bahawalpur, Pakistan

Li-Co spinal ferrites were synthesized in pure and doped form by substituting/doping a post transition metal, bismuth in varying concentrations using micro-emulsion technique.

Effect of bismuth substitution was studied by investigating the structural and magnetic properties in detail. X-ray diffractometer results confirmed the creation of single phase along with a slight occurrence of orthophase in prepared ferrites. Average crystallite size increased from 14 to 28 nm by increase in bismuth concentration. SEM micrographs were in complete agreement with XRD results showing spherical to cubic grains which was a confirmation of cubic spinal structure. Average estimated grain size of 52 nm showing agglomeration was also a good testimony of XRD results. VSM technique was employed to study magnetic properties of prepared samples within applied magnetic field strength of

-10,000Oe to 10,000Oe. Ms and Hc values were observed to be decreasing with increasing bismuth content. Lower Ms and Hc values made our newly synthesized material fit for transformer cores and induction purposes.