Spin Crossover Complexes Of Iron Series With Regard To Transport Characteristics

The downsizing of electrical gadgets is a constant development in today’s technological world.It is a useful method for enhancing the performance of electronic devices and circuit integration.Traditional silicon-based electronic devices,on the other hand,are getting close to their limits in terms of physical laws,fabrication methods,and energy usage as device sizes get closer to the nanoscale or even get smaller.One of the current research topics is the construction of molecular spin electronic devices with specialized functionality employing molecules as the functional core and the spin characteristics of electrons as a means of overcoming the limitations of conventional silicon-based electronic devices.Molecular spin electronic devices have a wide range of application possibilities and advantages over conventional silicon-based devices,including greater data capacity,smaller volume,reduced energy consumption,and faster response speed.When exposed to an external electric field,spin crossover（SCO）materials can exhibit bistability at the molecular level close to ambient temperature.As a result,these kinds of molecules could be used in molecular switches,displays,and storage systems.The spin transport properties of six-coordination Fe（II）-SCO complexes,also known as Fe（II）-N₆-SCO,were studied in this paper using density functional theory（DFT）and non-equilibrium green’s function（NEGF）,and practical molecular spintronic devices,including spin filters,molecular switches,and negative differential resistance devices,were developed.The following study findings are presented in this paper:1.The Fe（II）-N₆-SCO complex sandwiched between two Au（100）electrodes was examined for its spin transport characteristics.According to the findings,the highest value of 1.77μA for the current through the low spin（LS）molecular junction indicates that it increases gradually but only little over a range of applied biases.In comparison to the LS state,the current across the high spin（HS）molecular junction is significantly higher.Moreover,the spin-up current（I_↑）is significantly smaller than the spin-down current（I_↓）in the HS condition.The spin-down electrons regulate the HS state’s transport property,and the molecular device exhibits spin filtering behavior as shown by the current ratio’s range of 310 to 2161.Also,as the bias rises,the spin-down current rises as well,peaking at 0.9 V（5.99μA）,and then gradually declining,producing a negative differential resistance effect（NDR）.Two NCSe ligands were converted into NCS,and after that,transport properties were examined to investigate the impact of altered central molecules on those properties.The NCS device’s current increases marginally at LS but remains low throughout the bias range,peaking at 2.74μA.Since the spin-down current in the HS state is significantly greater than the spin-up current,spin-down electrons are responsible for producing the HS state’s current.Compared to NCSe,the present ratio’s range is wider,ranging from 425 to 2740.The configuration of the HS state includes the effects of spin filtering and negative differential resistance.NCS devices have I-V curves that are quite similar to NCSe,but with somewhat higher current ratios and greater spin filtering effects.To sum up,Fe（II）-N₆-SCO complexes can be created as molecular switches,negative differential resistance devices,and spin filters,and they can enhance the performance of the developed molecular devices by changing the central molecules.2、The spin transport characteristics of the Fe（II）-N₆-SCO complex based on Ni electrode have been investigated since the magnetization of metal Ni electrodes may be adjusted by applying an external magnetic field.The findings demonstrate that（1）for voltages between 0.2 and 0.5 V in the HS state,the parallel（P）configuration’s current is significantly greater than that of the antiparallel（AP）configuration.As a result,the huge magnetoresistance effect is produced,and at a voltage of 0.3 V,the ratio can reach a maximum of 170.（2）The current value exhibits a slight rising phenomena in the LS state when the electrode’s magnetization is set to a P or AP spin structure,but the current value is always kept at a very low level.The HS state’s P and AP configurations both showed the spin filtering effect.The spin filtering efficiency was near to 100%,and spin-down electrons were in charge of controlling the current.In the p-spin arrangement,the spin-down current increases quickly when the voltage is higher than 0.1 V,reaches its peak current（2.16μA）at 0.3 V,and then rapidly decreases when the bias voltage is higher than 0.3 V,demonstrating an NDR effect.In the AP spin arrangement,the spin-down current climbs quickly above 0.4 V,peaks at 0.7 V at 3.19μA,and then rapidly decreases above 0.7 V,demonstrating an NDR effect.According to the aforementioned data,it is feasible to create a comprehensive spintronic functional device that combines the NDR effect and spin filtering effect using ferromagnetic Ni electrodes and such spin crossing molecules.In the HS arrangement,the huge magnetoresistance effect is produced by varying the magnetic field.