GROWTH OF GIANT MAGNETORESISTANCE THIN FILM OF CoFe2O4 AND ITS CHARACTERIZATION

• Main Author: (NIM : 30208003); Tim Pembimbing : Prof. Dr.-Ing. Mitra; Djamal Prof. Dr. Eng. Khairurrijal, RAMLI
• Format: Dissertations
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/19220
• Institution: Institut Teknologi Bandung

In this dissertation, we report the results of experimental studies on the development of giant magnetoresistance (GMR) thin film based on CoFe2O4 <br /> <br /> <br /> material. The purpose of this research is developed of the GMR thin films based on CoFe2O4 material and investigate the GMR effect. The GMR thin film, i.e.; <br /> <br /> <br /> sandwich (CoFe2O4/CuO/ CoFe2O4), spin valve (FeMn/CoFe2O4/CuO/CoFe2O4), and organic GMR (CoFe2O4/Alq3/CoFe2O4) have been deposited by dc-Opposed-Target Magnetron Sputtering (dc-OTMS) method onto Si (111) substrate. The deposition parameters are; time of growth was varied (corresponding to GMR <br /> <br /> <br /> thickness), flow rate of Argon gas of 100 sccm, deposition pressure of 5.4 x10-1 Torr, plasma voltage of 600 volts and growth temperature of 100oC. The crystalline structure and morphology of thin films were characterized by xray diffraction (XRD) and scanning electron microscope (SEM). The electrical properties were characterized using a four-point probe and magnetic properties were characterized using a vibrating sample magnetometer (VSM). <br /> <br /> <br /> Time of growth will affect the CoFe2O4 and CuO thin film thickness. Thin film thickness increases with increasing time of growth. The GMR ratio is influenced by CuO and CoFe2O4 layer thickness The GMR ratio decreases with increasing of the CuO layer thickness. When the CuO layer thickness increases, the conductivity through the GMR layer becomes very dominant and spin-dependent <br /> <br /> <br /> scattering is not effective, so the GMR ratio is reduced. However, the reduced value of the GMR ratio is not linear, but follows the pattern of damped oscillations. The CoFe2O4 layer thickness affects the GMR ratio, where the GMR ratio increased with increasing CoFe2O4 thickness, for thickness less than 62 nm. <br /> <br /> <br /> However, when the CoFe2O4 layer thickness is greater than 62.5 nm, the value of the GMR ratio is decreases with increasing the CoFe2O4 thickness. This is due to <br /> <br /> <br /> the appearance an inactive part in the CoFe2O4 layers which shunt the current, and will reduce the GMR ratio. The maximum value of GMR ratio obtained from the sandwich structure CoFe2O4/CuO/CoFe2O4 is 70% of CoFe2O4 layer thickness of 62 nm and CuO layer thickness of 14 nm. <br /> <br /> <br /> The growth of GMR thin film with a spin valve structure has been done to determine the effect of the antiferromagnetic layer to the GMR ratio. The spin <br /> <br /> <br /> valve structure consists of sandwich layers that given antiferromagnetic layer, FeMn. The CoFe2O4 and CuO layer thickness were fixed i.e: 48 nm and 14 nm, respectively. While FeMn layer thickness were varied from 30 nm to 60 nm. The maximum GMR ratio of the spin valve structure is obtained by 32% at FeMn layer thickness of 45 nm. <br /> <br /> <br /> To investigate the effect of the organic material as a spacer layer on the GMR ratio, we prepare the of CoFe2O4/Alq3/CoFe2O4 thin film. The maximum value of <br /> <br /> <br /> the GMR ratio of approximately 36% at room temperature was obtained for 15 minutes time of growth.