The equilibrium lattice parameter, heat capacity, thermal expansion coefficient and bulk modulus of Ni2MnGa Heusler alloy are successfully obtained using the first-principles plane-wave pseudopotential （PW-PP） metho...The equilibrium lattice parameter, heat capacity, thermal expansion coefficient and bulk modulus of Ni2MnGa Heusler alloy are successfully obtained using the first-principles plane-wave pseudopotential （PW-PP） method as well as the quasi-harmonic Debye model. We analyse the relationship between bulk modulus B and temperature T up to 800 K and obtain the relationship between bulk modulus B and pressure at different temperatures. It is found that the bulk modulus B increases monotonically with increasing pressure and decreases with increasing temperature. The pressure dependence of heat capacity Cv and thermal expansion α at various temperatures are also analysed. Finally, the Debye temperature of Ni2MnGa is determined from the non-equilibrium Gibbs function. Our calculated results are in excellent agreement with the experimental data.展开更多
The polycrystalline Ni_(48.2)Mn_(22.4) Ga_(29.4) alloys were prepared by means of melting in argon arc furnace.X-ray diffraction pattern indicates a fcc cubic structure with a lattice parameter of 0.5822nm at room tem...The polycrystalline Ni_(48.2)Mn_(22.4) Ga_(29.4) alloys were prepared by means of melting in argon arc furnace.X-ray diffraction pattern indicates a fcc cubic structure with a lattice parameter of 0.5822nm at room temperature.The phase transformation temperatures were:1℃for martensite start temperature,-11℃for martensite finish temperature,3℃for austenite start temperature and 11℃for austenite start temperature,respectively.The results showed that the effect of magnetic field on the strains increases with the decrease of temperature.A strain of 2.1×10^(-4)was obtained with an applied magnetic field of 5 kOe at-66℃.展开更多
An ultra-thin Co2MnSi(0.5 nm)/Mn Ga(1.5 nm) bilayer capped with Pt(5 nm) has been successfully grown by molecular-beam epitaxy.It is a potential candidate of synthetic antiferromagnets due to antiferromagnetic couplin...An ultra-thin Co2MnSi(0.5 nm)/Mn Ga(1.5 nm) bilayer capped with Pt(5 nm) has been successfully grown by molecular-beam epitaxy.It is a potential candidate of synthetic antiferromagnets due to antiferromagnetic coupling between Co2MnSi and MnGa,which is a promising skyrmion-racetrack-memory medium without skyrmion Hall effect after capping with a Pt layer.Unusual humps in transverse Hall resistance loops are clearly observed in the temperature range from 260 to 400 K.This anomaly is generally attributed to topological Hall effect,but other than that,we prove that non-uniform rotation of magnetic moments in the bilayer with magnetic field sweeping is also a possible mechanism contributed to the unusual hump.展开更多
基金supported by the National Natural Science Foundation of China (Grant No 60777012)the Program for Science &Technology Innovation Talents in Universities of Henan Province of China (Grant No 2008HASTIT008) the Science and Technology Foundation of Henan Province, China (Grant No 082300410050)
文摘The equilibrium lattice parameter, heat capacity, thermal expansion coefficient and bulk modulus of Ni2MnGa Heusler alloy are successfully obtained using the first-principles plane-wave pseudopotential （PW-PP） method as well as the quasi-harmonic Debye model. We analyse the relationship between bulk modulus B and temperature T up to 800 K and obtain the relationship between bulk modulus B and pressure at different temperatures. It is found that the bulk modulus B increases monotonically with increasing pressure and decreases with increasing temperature. The pressure dependence of heat capacity Cv and thermal expansion α at various temperatures are also analysed. Finally, the Debye temperature of Ni2MnGa is determined from the non-equilibrium Gibbs function. Our calculated results are in excellent agreement with the experimental data.
基金Supported by the National Natural Science Foundation of China under Grant No.59731030.
文摘The polycrystalline Ni_(48.2)Mn_(22.4) Ga_(29.4) alloys were prepared by means of melting in argon arc furnace.X-ray diffraction pattern indicates a fcc cubic structure with a lattice parameter of 0.5822nm at room temperature.The phase transformation temperatures were:1℃for martensite start temperature,-11℃for martensite finish temperature,3℃for austenite start temperature and 11℃for austenite start temperature,respectively.The results showed that the effect of magnetic field on the strains increases with the decrease of temperature.A strain of 2.1×10^(-4)was obtained with an applied magnetic field of 5 kOe at-66℃.
基金Supported by the National Program on Key Basic Research Project under Grant No.2018YFB0407601the Strategic Priority Research Program of the Chinese Academy of Sciences under Grant Nos.XDB44000000 and QYZDY-SSW-JSC015the National Natural Science Foundation of China under Grant Nos.11874349 and 11774339。
文摘An ultra-thin Co2MnSi(0.5 nm)/Mn Ga(1.5 nm) bilayer capped with Pt(5 nm) has been successfully grown by molecular-beam epitaxy.It is a potential candidate of synthetic antiferromagnets due to antiferromagnetic coupling between Co2MnSi and MnGa,which is a promising skyrmion-racetrack-memory medium without skyrmion Hall effect after capping with a Pt layer.Unusual humps in transverse Hall resistance loops are clearly observed in the temperature range from 260 to 400 K.This anomaly is generally attributed to topological Hall effect,but other than that,we prove that non-uniform rotation of magnetic moments in the bilayer with magnetic field sweeping is also a possible mechanism contributed to the unusual hump.
