Microstructure and electric property of MgO/Fe/MgO tri-layer films forming a nano-granular system

For tunneling magnetoresistance (TMR) devices using ferromagnetic nano particle films, the size, dispersion and number of nano particles are important factors. Relating to this, single layered Fe films (thickness: t = 0.5 – 10.0 nm) sandwiched between two MgO (2 nm thick) layers were fabricated by molecular beam epitaxy. By depositing at Ts = RT (room temperature), the Fe layer had an isolated island structure for less than 1 nm thick. Correspondingly, the negative magnetoresistance effect was observed, which is characteristic of TMR. By increasing Ts, the resistivity and the magnetoresistance (MR) ratio was increased. In this study, it was found that the optimal parameters for the growth of nano particle MgO/Fe/MgO based films are t = 0.5 – 1.0 nm and Ts = RT − 120 °C.