Study On Ferromagnetic And Ferroelectric Properties Of Nanowires And Their Performance Control

Nanomaterials refer to the materials with at least two dimensions in the three-dimensional space in the nanometer scale,and have attracted great attention due to their excellent physical and chemical properties.The development of nano-magnetic materials has not only enriched the experimental and theoretical research,but also brought profound influence on the development of spintronics.Nano-ferroelectric chips have the characteristics of non-volatile,fast data exchange and large data storage,and have a wide range of application prospects.However,studies on ferromagnetism and ferroelectricity of nanomaterials are still limited.Based on first-principles calculation,this paper mainly studies the design and performance of nano-ferromagnetic and ferroelectric materials,analyzes the geometric structure,stability,ferromagnetic and ferroelectric properties of materials,and provides an ideal platform for the design of high-efficiency and low-loss devices.First,we propose that chromium nitride（Cr N）is a ferromagnetic semi-metal that can produce a fully spin polarized current.In addition,the semi-gold property is further verified by more accurate HSE06 functional.The molecular dynamics simulation and phonon spectrum calculation show the thermodynamic and kinetic stability of Cr N.The results of cohesion energy and formation energy also prove the stability of the structure.The maximum valence band（VBM）and minimum conduction band（CBM）in the spin-down channel are determined by the N-p and Cr-d orbitals,respectively.The ferromagnetic semi-gold property of Cr N is provided by the partially occupied Cr-d orbit,where the semi-metallic gap（Δs）reaches 1.58 e V.The ferromagnetism in Cr N nanostructures is attributed to the superexchange interaction between magnetic Cr atoms,and considerable magnetocrystalline anisotropy energy（MAE）is obtained,with a maximum value of 0.40 me V per unit cell.In addition,lateral stretching of Cr N can effectively regulateΔs and MAE while maintaining semi-gold properties.The nanocable was designed by encapsulating Cr N in boron nitride（BN）nanotubes and retaining the magnetic and electronic properties of Cr N.These new properties make Cr N an excellent candidate structure for the development of high-performance spintronic devices.Secondly,the chip made of ferroelectric material has the advantages of long life,rich functions,and can guarantee the data stored after power failure.We designed a germanium nitride（Ge N）structure with spontaneous polarization.The optimized Ge N has a spontaneous polarization size of 8.03μC/cm²,and has excellent kinetic and thermodynamic stability.Ge N is a semiconductor structure with a band gap of 1.16 e V.It is found that the spontaneous polarization increases with the increase of stress.We have designed possible experimental fabrication of Ge N using carbon nanotube（CNT）as a container and found that it retains good ferroelectric properties.In addition,we calculate the carrier mobility of Ge N and find that if Ge N changes from a ferroelectric to a paramelectric phase,the mobility of the hole incr-eases while the mobility of the electron changes little.Therefore,hole mobility in Ge N is closely related to polarization displacement.Finally,we predict a nanowire with both ferromagnetic and ferroelectric properties,namely Mo OCl₃,which is a semiconductor structure with a band gap of 1.14me V.It has good kinetic stability in both ferroelectric phase and antiferroelectric phase.It is found that its spontaneous polarization is 9.43μC/cm²,which is the mixture of the Mo⁵⁺empty d orbital and the p orbital of O^2-along the polarity direction,and dominates the ferroelectric phase state in Mo OCl₃.Based on Monte Carlo simulation,the Curie temperature of Mo OCl₃is 277 K,close to room temperature.For ferromagnetism,the ground state of ferromagnetism is calculated,and the magnetism is provided by the transition metal Mo atom.The magnetic moment in each cell is 2μ_Band remains constant when a stress of-6%to 6%is applied.Our findings suggest a new class of materials for the development of miniaturized and high-density electronic devices.