We examine the electronic and magnetic structures of iron telluride KFe2Te2 using first-principle calculations. We demonstrate that the ground state of this compound is in bicollinear antiferromag- netic order with Fe...We examine the electronic and magnetic structures of iron telluride KFe2Te2 using first-principle calculations. We demonstrate that the ground state of this compound is in bicollinear antiferromag- netic order with Fe local moments （- 2.6 μB） that are ferromagnetically aligned along a diagonal direction and antiferromagnetically aligned along the other diagonal in the Fe-Fe square lattice, sim- ilar to the alignment discovered in the parent compound of superconductor α-FeTe. This bicollinear antiferromagnetic order results from the interplay among the nearest, next-nearest, and next-next- nearest neighbor exchange interactions, which are mediated by Te 5p orbitals. This finding may aid our understanding of the interplay between magnetism and superconductivity in the family of iron-based materials.展开更多
As a two-dimensional material with a hollow hexatomic ring structure,Néel-type anti-ferromagnetic(AFM)GdI_(3)can be used as a theoretical model to study the effect of electron doping.Based on first-principles cal...As a two-dimensional material with a hollow hexatomic ring structure,Néel-type anti-ferromagnetic(AFM)GdI_(3)can be used as a theoretical model to study the effect of electron doping.Based on first-principles calculations,we find that the Fermi surface nesting occurs when more than 1/3 electron per Gd is doped,resulting in the failure to obtain a stable ferromagnetic(FM)state.More interestingly,GdI_(3)with appropriate Mg/Ca doping(1/6 Mg/Ca per Gd)turns to be half-metallic FM state.This AFM–FM transition results from the transfer of doped electrons to the spatially expanded Gd-5d orbital,which leads to the FM coupling of local half-full Gd-4f electrons through 5d–4f hybridization.Moreover,the shortened Gd–Gd length is the key to the formation of the stable ferromagnetic coupling.Our method provides new insights into obtaining stable FM materials from AFM materials.展开更多
The influence of heavy samarion （Sm） doping （0.40≤x≤0.60） on magnetic and electric properties of La0.67-xSmxSr0.33MnO3 was investigated by measuring the magnetization-temperature （M - T） curves, magnetization-...The influence of heavy samarion （Sm） doping （0.40≤x≤0.60） on magnetic and electric properties of La0.67-xSmxSr0.33MnO3 was investigated by measuring the magnetization-temperature （M - T） curves, magnetization-magnetic density （ M - H） curves, resistivity-temperature （ρ- T） curves and magnetoresistivity-temperature （ MR - T） curves of the samples under different temperatures. It is found that, form from long-range ferromagnetic order to spin-cluster glass with the increase of Sm doping amount, the samples transstate and anti-ferromagnetic state; and when x = 0.60, the transport property becomes abnormal under magnetic background; and the magnetic structure changes and extra magnetic coupling induced by doping leads to colossal magnetoresistance effect. The transport mechanism of metallic conduction at low temperature is mainly electron-magneton interaction and can be fitted by the formula ρ = ρ0 ＋ AT^4.5, and the insulatorlike transport mechanism on high temperature range is mainly the function of variable-range hopping and can be fitted by the formula ρ = ρ0exp（T0/T）^1/4. In the formulas above, p is resistivity, T is temperature, and A, ρ0, T0 are constants.展开更多
Mn Fe2O4nanoparticles were synthesized by thermal decomposition of a metal–organic salt in organic solvent with a high boiling point.Some nanoparticles exhibited the triangular shape which has not been observed befor...Mn Fe2O4nanoparticles were synthesized by thermal decomposition of a metal–organic salt in organic solvent with a high boiling point.Some nanoparticles exhibited the triangular shape which has not been observed before as far as we know,while some nanoparticles formed the aggregates with different sizes and shapes.The strength of interparticle dipolar interaction was changed by diluting Mn Fe2O4nanoparticles in the SiO2 matrix with different concentrations.The strong dipolar interaction has been suggested to enhance the blocking temperature（TB）and suppress the remanence（Mr）to saturation（Ms）magnetization ratio（Mr/Ms）for the spherical-like cobalt ferrite nanoparticles in many previous reports.However,Mr/Msand TBof Mn Fe2O4 nanoparticles reported herein mainly depend on the size and shape of the nanoparticles and their aggregates.展开更多
In this Letter, ceramic Nd：YAG is charactrizeby electron spin resonance （ESR） measurements. The ESR results indicate that the polycrystalline ceramic Nd：YAG has barely native defects and impurity ions localization...In this Letter, ceramic Nd：YAG is charactrizeby electron spin resonance （ESR） measurements. The ESR results indicate that the polycrystalline ceramic Nd：YAG has barely native defects and impurity ions localization defects, compared to an Nd：YAG crystal with the same Nd doping concentration, due to its density structure by sintering in a vacuum pure raw material and additives during the fabrication. It may conclude that the high quality ceramic Nd：YAG may have greater ability on optical characteristic, mechanical performance, and laser damage than that of the crystals, which is a promising candidate to use on laser diode-pumped solid-state lasers.展开更多
文摘We examine the electronic and magnetic structures of iron telluride KFe2Te2 using first-principle calculations. We demonstrate that the ground state of this compound is in bicollinear antiferromag- netic order with Fe local moments （- 2.6 μB） that are ferromagnetically aligned along a diagonal direction and antiferromagnetically aligned along the other diagonal in the Fe-Fe square lattice, sim- ilar to the alignment discovered in the parent compound of superconductor α-FeTe. This bicollinear antiferromagnetic order results from the interplay among the nearest, next-nearest, and next-next- nearest neighbor exchange interactions, which are mediated by Te 5p orbitals. This finding may aid our understanding of the interplay between magnetism and superconductivity in the family of iron-based materials.
基金supported by the National Key Research and Development Program of China(No.2022YFB3807203)the National Natural Science Foundation of China(Nos.22033002 and 21973011).
文摘As a two-dimensional material with a hollow hexatomic ring structure,Néel-type anti-ferromagnetic(AFM)GdI_(3)can be used as a theoretical model to study the effect of electron doping.Based on first-principles calculations,we find that the Fermi surface nesting occurs when more than 1/3 electron per Gd is doped,resulting in the failure to obtain a stable ferromagnetic(FM)state.More interestingly,GdI_(3)with appropriate Mg/Ca doping(1/6 Mg/Ca per Gd)turns to be half-metallic FM state.This AFM–FM transition results from the transfer of doped electrons to the spatially expanded Gd-5d orbital,which leads to the FM coupling of local half-full Gd-4f electrons through 5d–4f hybridization.Moreover,the shortened Gd–Gd length is the key to the formation of the stable ferromagnetic coupling.Our method provides new insights into obtaining stable FM materials from AFM materials.
文摘The influence of heavy samarion （Sm） doping （0.40≤x≤0.60） on magnetic and electric properties of La0.67-xSmxSr0.33MnO3 was investigated by measuring the magnetization-temperature （M - T） curves, magnetization-magnetic density （ M - H） curves, resistivity-temperature （ρ- T） curves and magnetoresistivity-temperature （ MR - T） curves of the samples under different temperatures. It is found that, form from long-range ferromagnetic order to spin-cluster glass with the increase of Sm doping amount, the samples transstate and anti-ferromagnetic state; and when x = 0.60, the transport property becomes abnormal under magnetic background; and the magnetic structure changes and extra magnetic coupling induced by doping leads to colossal magnetoresistance effect. The transport mechanism of metallic conduction at low temperature is mainly electron-magneton interaction and can be fitted by the formula ρ = ρ0 ＋ AT^4.5, and the insulatorlike transport mechanism on high temperature range is mainly the function of variable-range hopping and can be fitted by the formula ρ = ρ0exp（T0/T）^1/4. In the formulas above, p is resistivity, T is temperature, and A, ρ0, T0 are constants.
基金supported by the National Natural Science Foundation of China (Grant Nos.51471001,11174004 and 11304001)
文摘Mn Fe2O4nanoparticles were synthesized by thermal decomposition of a metal–organic salt in organic solvent with a high boiling point.Some nanoparticles exhibited the triangular shape which has not been observed before as far as we know,while some nanoparticles formed the aggregates with different sizes and shapes.The strength of interparticle dipolar interaction was changed by diluting Mn Fe2O4nanoparticles in the SiO2 matrix with different concentrations.The strong dipolar interaction has been suggested to enhance the blocking temperature（TB）and suppress the remanence（Mr）to saturation（Ms）magnetization ratio（Mr/Ms）for the spherical-like cobalt ferrite nanoparticles in many previous reports.However,Mr/Msand TBof Mn Fe2O4 nanoparticles reported herein mainly depend on the size and shape of the nanoparticles and their aggregates.
文摘In this Letter, ceramic Nd：YAG is charactrizeby electron spin resonance （ESR） measurements. The ESR results indicate that the polycrystalline ceramic Nd：YAG has barely native defects and impurity ions localization defects, compared to an Nd：YAG crystal with the same Nd doping concentration, due to its density structure by sintering in a vacuum pure raw material and additives during the fabrication. It may conclude that the high quality ceramic Nd：YAG may have greater ability on optical characteristic, mechanical performance, and laser damage than that of the crystals, which is a promising candidate to use on laser diode-pumped solid-state lasers.
