Conductive filament nanostructures and their magnetization reversal in NiO resistive switching memory cells

We demonstrate that conductive filament (CF) nanostructures in NiO thin film resistive switching memory (RRAM) cells present unique magnetic properties. The CF nanostructures of nanodots and nanorods formed using a conductive atomic force microscopy tip were fabricated through the forming process of CFs for the NiO RRAM cells. In the current-voltage curve, unipolar resistive switching behavior was observed. The ferromagnetic domain and magnetization switching of CF nanostructures were characterized using magnetic force microscopy. In principle, nanoscale-sized magnetic nanostructures possess superparamagnetism due to their thermal fluctuations. In this study, however, CF nanorods with a length of 30 nm exhibited ferromagnetism because the exchange bias effect occurred at the interface between the antiferromagnetic NiO and the CF nanorod. Therefore, the ferromagnetism of the CF nanostructures is the origin of the magnetization switching and can be favorable in magnetic storage device applications by overcoming the superparamagnetic limits with the exchange bias effect.