Resistive Switching in oxides has offered new opportunities for developing resistive random access memory (ReRAM) devices. Here we demonstrated bipolar Resistive Switching along with magnetization switching of cobalt ferrite (CFO) thin film using Al/CFO/FTO sandwich structure, which makes it a potential candidate for developing future multifunctional memory devices. The device shows good retention characteristic time (>104 seconds) and endurance performance, a good resistance ratio of high resistance state (HRS) and low resistance state (LRS) ~103. Nearly constant resistance values in LRS and HRS confirm the stability and non-volatile nature of the device. The device shows different conduction mechanisms in the HRS and LRS i.e. Schottky, Poole Frenkel and Ohmic. Magnetization of the device is also modulated by applied electric field which has been attributed to the oxygen vacancies formed/annihilated during the voltage sweep and indicates the presence of valence change mechanism (VCM) in our device. It is suggested that push/pull of oxygen ions from oxygen diffusion layer during voltage sweep is responsible for forming/rupture of oxygen vacancies conducting channels, leading to switching between LRS and HRS and for switching in magnetization in CFO thin film. Presence of VCM in our device was confirmed by X-ray Photoelectron Spectroscopy at Al/CFO interface.

Among the emerging memories, resistive switching (RS) based resistive random-access memories (RRAMs) are attracting lots of attention due to their simple metal–insulator–metal structures, low power consumption, long endurance and retention characteristics, low fabrication cost, ultrafast switching, and CMOS compatibility. In recent years, several oxides, chalcogenides, polymers and their composites have been explored for RS devices. Many of these studies show a high resistance ratio of the OFF and ON states with good RS characteristics. Some of these studies also show the realization of multifunctional RS devices such as the simultaneous switching of resistance and magnetic states. In order to scale up RS-based RRAMs, a detailed understanding of the occurrence of RS is very much desirable. In this review, we provide an overview of the current understanding, recent advances and future outlook of RS-based RRAM devices along with fundamental concepts of the different types of RS, and conventional as well as novel measurement techniques which are being used to characterize RS devices. Observations of RS in different materials are presented, and RS mechanisms, such as the valence change mechanism and electrochemical metallization memory, are discussed in detail. An overview of multifunctional RS devices and the main challenges faced in scaling up RS devices is also presented.

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Single phase cobalt ferrite (CoFe2O4, CFO) nanoparticles of a controlled size (~ 6 nm) exhibiting superparamagnetic properties have been synthesized by hydrothermal technique using oleic acid (OA) as surfactant. The oleic acid coated CFO nanoparticles are stable in nonpolar organic media, such as hexane but are not well dispersible in water. The surface of these snanoparticles has been further modified by citric acid using ligand exchange process, which makes CFO nanoparticles more stable colloidal solution in water. Citric acid coated CFO nanoparticles exhibits high dispersibility in water, high zeta potential, very low coercivity and moderate saturation magnetization. Biocompatibility of these CFO nanoparticles is demonstrated through cytotoxicity test in L929 cell line.

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