The electronic band structure and optical parameters of SnMg_(2)O_(4) are investigated by the first-principles technique based on a new potential approximation known as modified Becke–Johnson(mBJ).The direct band gap...The electronic band structure and optical parameters of SnMg_(2)O_(4) are investigated by the first-principles technique based on a new potential approximation known as modified Becke–Johnson(mBJ).The direct band gap values by LDA,GGA and EV-GGA are underestimated significantly as compared to mBJ-GGA,which generally provides the results comparable to the experimental values.Similarly,the present band gap value(4.85 eV)using mBJ-GGA is greatly enhanced to the previous value by EV-GGA(2.823 eV).The optical parametric quantities(dielectric constant,index of refraction,reflectivity,optical conductivity and absorption coefficient)relying on the band structure are presented and examined.The first critical point(optical absorption's edge)in SnMg_(2)O_(4) occurs at about 4.85 eV.A strong absorption region is observed,extending between 5.4 eV to 25.0 eV.For SnMg_(2)O_(4),static dielectric constantε1(0),static refractive index n(0),and the magnitude of the coefficient of reflectivity at zero frequency R(0)are 2.296,1.515 and 0.0419,respectively.The optoelectronic properties indicate that this material can be successfully used in optical devices.展开更多
The low magnetic moment （MM） in diluted magnetic semiconductors （DMS） at low impurity doping levels has triggered considerable research into condensed magnetic semiconductors （CMS）.This work reports an ab-initio...The low magnetic moment （MM） in diluted magnetic semiconductors （DMS） at low impurity doping levels has triggered considerable research into condensed magnetic semiconductors （CMS）.This work reports an ab-initio investigation of the electronic structures and magnetic properties of ZnO in a zinc-blende （ZB） structure doped with nickel ions. Ni-doped ZnO-based DMS and CMS exhibit a dominance of ferromagnetic coupling over antiferromagnetic. A robust increase in the magnetization has been observed as a function of Ni impurity levels. This material favors short-range magnetic interactions at the ground state, suggesting that the observed ferromagnetism is defined by the double exchange mechanism. The spin-polarized density of states （DOS） of Ni-doped ZnO characterizes it as half-metallic with a considerable energy gap for up-spin components and as metallic for-down spins. Half metallic Ni：ZnO based magnetic semiconductors with high magnetization are expected to have potential applications in spintronics.展开更多
基金Supported by the Fund for Foreign Academic Visitors of Universiti Teknologi Malaysia(UTM)Skudai,Johor,Malaysia under Grant No JI3000077264D035.
文摘The electronic band structure and optical parameters of SnMg_(2)O_(4) are investigated by the first-principles technique based on a new potential approximation known as modified Becke–Johnson(mBJ).The direct band gap values by LDA,GGA and EV-GGA are underestimated significantly as compared to mBJ-GGA,which generally provides the results comparable to the experimental values.Similarly,the present band gap value(4.85 eV)using mBJ-GGA is greatly enhanced to the previous value by EV-GGA(2.823 eV).The optical parametric quantities(dielectric constant,index of refraction,reflectivity,optical conductivity and absorption coefficient)relying on the band structure are presented and examined.The first critical point(optical absorption's edge)in SnMg_(2)O_(4) occurs at about 4.85 eV.A strong absorption region is observed,extending between 5.4 eV to 25.0 eV.For SnMg_(2)O_(4),static dielectric constantε1(0),static refractive index n(0),and the magnitude of the coefficient of reflectivity at zero frequency R(0)are 2.296,1.515 and 0.0419,respectively.The optoelectronic properties indicate that this material can be successfully used in optical devices.
文摘The low magnetic moment （MM） in diluted magnetic semiconductors （DMS） at low impurity doping levels has triggered considerable research into condensed magnetic semiconductors （CMS）.This work reports an ab-initio investigation of the electronic structures and magnetic properties of ZnO in a zinc-blende （ZB） structure doped with nickel ions. Ni-doped ZnO-based DMS and CMS exhibit a dominance of ferromagnetic coupling over antiferromagnetic. A robust increase in the magnetization has been observed as a function of Ni impurity levels. This material favors short-range magnetic interactions at the ground state, suggesting that the observed ferromagnetism is defined by the double exchange mechanism. The spin-polarized density of states （DOS） of Ni-doped ZnO characterizes it as half-metallic with a considerable energy gap for up-spin components and as metallic for-down spins. Half metallic Ni：ZnO based magnetic semiconductors with high magnetization are expected to have potential applications in spintronics.
