The Study On The Spin Interface Of Saturated Alkane Carboxylic Acid Molecules Encapsulating Fe₃O₄ Nanoparticles

As a branch of spintronics,organic spintronics is a hottest platform for studying electron spins now.And it has many advantages that inorganic materials do not possess.On the one hand,the number of chemical elements in organic materials is small,so spin-orbit coupling and hyperfine interaction are weak,organic material has a long spin relaxation time,which is conducive to the transport and research of spin electrons.On the other hand,the composition of organic molecules and the diversity of structures make the properties of organic material rich and colorful.We will have more space for selecting suitable organic materials and improve the applicability of organic spin materials.In organic spintronic device,the interface between organic molecule and ferromagnetic electrode is particularly important in determining device performance,and the interface is also sensitive to environmental changes.A large number of experiments can prove that: different ferromagnetic/organic interfaces,the interface will have different ways of acting on the spintronics,which will cause the whole device to exhibit different magnetoresistance effects.And the different adsorption sites and modes between ferromagnetic metals and the organic molecules at the interface also change the properties of the spin devices.This fully demonstrates that the rich nature of the spin interface expands the practical range of application of organic spin devices.In order to study the spin interface,the magnetic tunneling network composed of saturated alkane carboxylic acid molecule encapsulated Fe₃O₄ nanoparticles was prepared by self-assembly method.Here,an organic monolayer was selected,and the advantage of the organic monolayer was to reduce the randomness of the spin electron transport path in the organic layer and simplify our subsequent study of the spin interface.Specifically,based on the magnetic tunneling network structure composed of saturated alkane carboxylic acid molecules wrapped with Fe₃O₄ nanoparticles,Fe₃O₄ was coated with different saturated alkane linear carboxylic acids to study how the magnetic and electrical transport of spintrons will differ in different tunneling barriers.In order to verify whether the interface of the prepared saturated alkane carboxylic acid molecules encapsulates Fe₃O₄ nanoparticles is stable,and to detect the influence of the oxygen content at the interface on the spintronic electron transport and electrical transport,we must first understand the specificity of the ferromagnetic and organic molecules at the interface adsorption method,Secondly,in the process of preparing the sample,nitrogen gas is introduced as a shielding gas to change the oxygen content of the interface of the organic molecule/Fe₃O₄ interface,then the resistivity and the magnitude of the magnetoresistance of the sample are detected,and compared with the results of the sample under non-nitrogen protection,the experimental conclusion was drawn.The experimental results show that the resistivity of saturated alkane linear carboxylic acid-coated Fe₃O₄ nanoparticles increases exponentially with the increase of C chain under non-nitrogen protection,which is a typical tunneling magnetoresistance effect.The length of the C chain has little effect on the magnetoresistance MR.In other words,the magnetoresistance of the different saturated alkane linear carboxylic acid-coated Fe₃O₄ nanoparticles is uniform.Under the condition of nitrogen protection,the resistivity of the saturated alkane linear carboxylic acid-coated Fe₃O₄ nanoparticles also shows the tunneling magnetoresistance effect,that is,the resistivity increases exponentially with the increase of the C chain.However,the resistivity of the sample under nitrogen protection was reduced by a factor of 1/3 compared to the sample resistivity under non-nitrogen protection.the magnetoresistance does not change significantly.Combined with these conclusions,it can be confirmed that the decrease of oxygen content at the interface of Fe₃O₄/organic molecules leads to an increase in the residual charge on the surface of Fe₃O₄ particles.A Fe₃O₄ nanoparticle combines with multiple organic molecules,making the transport channel more numerous,which is equivalent to parallel connection of resistance,but the spin interface does not change.The self-assembled Fe₃O₄ nanoparticles encapsulated with organic carboxylic acid were proved to be simple and stable,and it's suitable for studying the transport properties of spintrons.