230 J. Math. Fund. Sc i., Vol. 48, No. 3, 2016, 230-240 Received January 6 th , 2015, Revised August 9 th , 2016, Accepted for publication October 22 nd , 2016. Copyright © 2016 Published by ITB Journal Publisher, ISSN: 2337-5760, DOI: 10.5614/j.math.fund.sci.2016.48.3.4 Novel Ternary CoFe 2 O 4 /CuO/CoFe 2 O 4 as a Giant Magnetoresistance Sensor Ramli 1 , Ambran Hartono 2 , Edi Sanjaya 2 , Ahmad Aminudin 3 , Khairurrijal 4 , Freddy Haryanto 4 , Cuk Imawan 5 & Mitra Djamal 4,6 1 Department of Physics, Faculty of Mathematics and Natural Sciences, Universitas Negeri Padang, Jalan Prof. Hamka, Padang 25131, Indonesia 2 Department of Physics, Universitas Islam Negeri Syarif Hidayatullah Jakarta, Jalan Ir. H. Juanda 95, Ciputat, Banten 15412, Indonesia 3 Department of Physics Education, Faculty of Mathematics and Natural Sciences Universitas Pendidikan Indonesia, Jalan Dr. Setiabudi 229, Bandung 40154, Indonesia 4 Department of Physics, Faculty of Mathematics and Natural Sciences, Institut Teknologi Bandung, Jalan Ganesha 10, Bandung 40132, Indonesia 5 Department of Physics, Faculty of Mathematics and Natural Sciences, Universitas Indonesia, Kampus UI Depok, Jawa Barat 16424, Indonesia 6 Department of Physics, Institut Teknologi Sumatera, Jalan Terusan Jenderal Ryacudu, Lampung Selatan 35365, Indonesia E-mail: ramli@fmipa.unp.ac.id Abstract. This paper reports the results of a study relating to the synthesis of a novel ternary CoFe 2 O 4 /CuO/CoFe 2 O 4 thin film as a giant magnetoresistance (GMR) sensor. The CoFe 2 O 4 /CuO/CoFe 2 O 4 thin film was prepared onto silicon substrate via DC magnetron sputtering with the targets facing each other. X-ray diffraction was used to determine the structure of the thin film and a 4-point method was used to measure the MR ratio. The GMR ratio is highly dependent on the ferrimagnetic (CoFe 2 O 4 ) and nonmagnetic (CuO) layer thickness. The maximum GMR ratio at room temperature obtained in the CoFe 2 O 4 /CuO/CoFe 2 O 4 thin film was 70% when the CoFe 2 O 4 and the CuO layer had a thickness of 62.5 nm and 14.4 nm respectively. Keywords: CoFe 2 O 4 ; CuO; ferrimagnetic; giant magnetoresistance sensor; magnetic sensor; spintronics. 1 Introduction Recently, research on spintronic devices has developed very rapidly [1-4]. Spintronics is a new field that explores the effect of spin on the electronic transport in magnetic nanostructures. The discovery of GMR in 1988 [5,6] marked the birth of spintronics. The invention of GMR has opened up opportunities for application in various fields. Until now, a number of devices that work based on the phenomenon of GMR have been developed, such as magnetic field sensors [7,8], magnetic recording devices [9], and non-volatile memory [10]. The demand for the development of magnetic field sensors based