In this study, we present some results on the structure and properties of the solid solution of – BiFeCoO3 (BKT – BFCO) by Sol-gel method. Crystal structures of BKT – BFCO solid solutions were studies by XRD and Raman spectroscopy. | Vietnam Journal of Science and Technology 56 (1A) (2018) 197-203 FABRICATION AND PROPERTIES OF Co DOPED – BiFeO3 SOLID SOLUTION Nguyen Hoang Tuan*, Nguyen The Hoang, Nguyen Hoang Linh, Dang Duc Dung School of Engineering Physic, Hanoi University of Science and Technology, No. 1 Dai Co Viet st., Hai Ba Trung dist., Ha Noi. * Email: Received: 15 August 2017; Accepted for publication: 31 March 2018 ABSTRACT In this study, we present some results on the structure and properties of the solid solution of – BiFeCoO3 (BKT – BFCO) by Sol-gel method. Crystal structures of BKT – BFCO solid solutions were studies by XRD and Raman spectroscopy. The results were in good agreement with the previous reports of – BiFeO3 (BKT – BFO) and – BiCoO3 (BKT – BCO) solid solutions. The magnetic properties were investigated via unsaturated M-H loop, which showed the competition of paramagnetic and antiferromagnetic ordering in BKT – BFCO. However, differing from the BKT – BFO and BKT – BCO solid solutions, the unclear values of saturated magnetism in BKT – BFCO raised the unexplained question, which needed further studies. Keywords: sol-gel, BKT, ferroelectric, multiferroic, solid solutions. 1. INTRODUCTION Recently, much attention has been paid to multiferroic materials exhibiting simultaneously a combination of ferroelectric, ferromagnetic, and/or ferroelasticity behaviours. Also, the coupling effect of electrical and magnetic order parameters gives a rise to a wide range of novel applications, such as in magnetic sensors, transformers, multiple state memories and microwave devices [1–4]. Among all multiferroics, BiFeO3 (BFO) is well-known as one of the most promising materials for device applications due to its high Curie temperature (TC ~ 1103K) and antiferromagnetic temperature (TN ~ 643K) [5,6]. In BFO, the antiferromagnetic spin structure is G-type. This spatially modulated cycloidal spin structure .