The magnetoelectric characteristics of perpendicular magnetic thin film CoFeB MTJ embedded with Co dots

• Main Authors: Po-Jen Yang, 楊博任
• Other Authors: Te-Ho Wu
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/61874477995683421314

碩士 === 國立雲林科技大學 === 材料科技研究所 === 104 === This study focused on the magnetic tunnel junction(MTJ) structure embedded with various size of magnetic nanoparticles Co dots, and analysed their magnetoelectric properties. In this work, by controlling the deposition rate and the thickness of cobalt thin films, we fabricated the small cobalt nanoparticles embedded within the MgO layer. The resistivity and magnetic properties were measured by Van der pauw methods and Alternating Gradient Magnetometer(AGM), respectively. The microstructures of the samples were measured by Transmission Electron Microscopy(TEM). The samples with various thicknesses and annealing temperatures were patterned into different devices, and the tunneling magnetoresistance(TMR) ratio was measured with applied magnetic field by four-point-probe method. MTJ are fabricated containing Co nanoparticles in MgO insulating layer by stacking up method. The two-stages temperature annealing method are performed. The results show that when dopped with Co thickness exceeds 1.7 nm, due to increased in-plane magnetization, the perpendicular anisotropy will decrease, and show no double loop. When the Co film thickness exceeds 1.5 nm, its resistivity decreases significantly. Microstructure analysis by the TEM shows that, a large and dense particle size is formed when cobalt particle size is about1.4 nm.However, when Co thickness is between 1.5 nm to 1.7 nm, the particle discrete layer is change formed into continuous film. In this study, we founded that the insertion of cobalt nanoparticles in MTJs affects the magnetoresistance (MR) definitely.For the device of cell size 33 μm2, by inserting 1.1 nm cobalt thin film, the MR ratio can raise from 14.7 % up to 200 %.