Multilevel resistive and magnetization switching in Cu/CoFe2O4/Pt device: Coexistence of ionic and metallic conducting filaments

Abstract

Non-volatile, multilevel bipolar Resistive Switching (RS) along with multilevel magnetization switching, in a cobalt ferrite (CFO) thin film using a simple Cu/CFO/Pt sandwich structure, has been demonstrated. Besides the low resistance state (LRS) and the high resistance state (HRS), the device exhibits two intermediate resistance states (IRSs), which are stable with time and reproducible in RS cycles. The endurance characteristics of the present RS device (>500 switching cycles) show no noticeable degradation and the ultimate resistance ratio always remains >104, which ensures reproducibility, reversibility, and controllability of the RS features of the present device. The HRS of the device shows a semiconducting conduction mechanism, whereas the LRS and both the IRSs were found to be Ohmic in nature. Simultaneous magnetization and resistive switching confirmed the multifunctional behavior of the device and suggested the presence of a valence change mechanism of resistive switching. The magnetization vs. magnetic field studies and temperature dependent resistance studies revealed that the electrochemical metallization also plays an important role during the switching process, which enhances the resistance ratio by providing an additional metallic filament of Cu atoms along with the ionic conducting filament of oxygen vacancies. The voltage controlled multilevel magnetization and resistive switching with a large memory window (resistance ratio >104) make the present device a potential candidate for paving the path for future multifunctional and multilevel memory devices with the capability of high density data storage.