Chemical pressure induced by iso-valent doping has been widely employed to tune physical properties of materials. In this work, we report effects of chemical pressure by substitution of Sb or P into As on a recently d...Chemical pressure induced by iso-valent doping has been widely employed to tune physical properties of materials. In this work, we report effects of chemical pressure by substitution of Sb or P into As on a recently discovered diluted magnetic semiconductor(Ba,K)(Zn,Mn)_2 As_2, which has the record of reliable Curie temperature of 230 K due to independent charge and spin doping. Sb and P are substituted into As-site to produce negative and positive chemical pressures, respectively.X-ray diffraction results demonstrate the successful chemical solution of dopants. Magnetic properties of both K-underdoped and K-optimal-doped samples are effectively tuned by Sb-and P-doping. The Hall effect measurements do not show decrease in carrier concentrations upon Sb-and P-doping. Impressively, magnetoresistance is significantly improved from7% to 27% by only 10% P-doping, successfully extending potential application of(Ba,K)(Zn,Mn)_2 As_2.展开更多
A new compound with one-dimensional spin chains, Ba9Co3Se(15), was synthesized under high pressure and high temperature conditions and systematically characterized via structural, transport and magnetic measurements. ...A new compound with one-dimensional spin chains, Ba9Co3Se(15), was synthesized under high pressure and high temperature conditions and systematically characterized via structural, transport and magnetic measurements. Ba9Co3Se(15) crystallizes in a hexagonal structure with the space group P-6c2(No. 188) and lattice constants of a = b = 9.6765 ? and c = 18.9562 ?. The structure consists of trimeric face-sharing octahedral CoSe6 chains, which are arranged in a triangular lattice in the ab-plane and separated by Ba atoms. The distance of the nearest neighbor of CoSe6 chains is very large, given by the lattice constant a = 9.6765 ?. The Weiss temperature Tθ associated with the intra-chain coupling strength is about -346 K. However, no long-range magnetic order but a spin glass transition at ~ 3 K has been observed. Our results indicate that the spin glass behavior in Ba9Co3Se(15) mainly arises from the magnetic frustration due to the geometrically frustrated triangular lattice.展开更多
A series of samples of Ba_(9)Co_(3)(Se_(1−x)S_(x))_(15)(x=0,0.05,0.1,0.15,0.2)with quasi-one-dimensional(1D)structure were successfully synthesized under high-temperature and high-pressure conditions.The influence of ...A series of samples of Ba_(9)Co_(3)(Se_(1−x)S_(x))_(15)(x=0,0.05,0.1,0.15,0.2)with quasi-one-dimensional(1D)structure were successfully synthesized under high-temperature and high-pressure conditions.The influence of partial substitution of S for Se on the structure,electronic transport,and magnetic properties of Ba_(9)Co_(3)(Se_(1−x)S_(x))_(15) has been investigated in detail.The x-ray diffraction data shows that the lattice constant decreases linearly with increasing S-doping level,which follows the Vegrad’s law.The doped S atoms preferentially occupy the site of Se atoms in CoSe6 octahedron.Physical properties measurements indicate that all the samples of Ba_(9)Co_(3)(Se_(1−x)S_(x))_(15) are semiconducting and display spin glass behavior.As the replacement of Se by smaller size S,although the inter-chain distance decreases,the electronic hopping between CoSe/S6 chains is weakened and leads to an increase of band gap from 0.75 eV to 0.86 eV,since the S-3p electrons are more localized than Se-4p ones.Ba_(9)Co_(3)(Se_(1−x)S_(x))_(15) exhibits 1D conducting chain characteristic.展开更多
Recently,a series of novel compounds Ba3MX5(M=Fe,Ti,V;X=Se,Te)with hexagonal crystal structures composed of quasi-1-dimensional(1D)magnetic chains has been synthesized by our research team using high-pressure and high...Recently,a series of novel compounds Ba3MX5(M=Fe,Ti,V;X=Se,Te)with hexagonal crystal structures composed of quasi-1-dimensional(1D)magnetic chains has been synthesized by our research team using high-pressure and high-temperature methods.The initial hexagonal phases persist to the maximum achievable pressure,while spin configurations and magnetic interactions may change dramatically as a result of considerable reductions in interchain separations upon pressurization.These compounds therefore offer unique possibilities for studying the evolution of intrinsic electronic structures in quasi-1D magnetic systems.Here we present a systematic investigation of Ba9Fe3Te15,in which the interchain separations between trimerized 1D chains(~10.2Å)can be effectively modulated by external high pressure.The crystal structure especially along the 1D chains exhibits an abnormal expansion at^GPa,which accompanies trimerization entangled anomalous mixed-high-low spin transition.An insulator-metal transition has been observed under high pressure as a result of charge-transfer gap closing.Pressure-induced superconductivity emerges at 26 GPa,where the charge-transfer gap fully closes,3D electronic configuration forms and local spin fully collapses.展开更多
In La-Cr-As system,the first ternary compound La3CrAs5 has been successfully synthesized under highpressure and high-temperature conditions.La3CrAs5 crystallizes into a hexagonal Hf5Sn3Cu-anti type structure with a sp...In La-Cr-As system,the first ternary compound La3CrAs5 has been successfully synthesized under highpressure and high-temperature conditions.La3CrAs5 crystallizes into a hexagonal Hf5Sn3Cu-anti type structure with a space group of P63/mcm(No.193)and lattice parameters of a=b=8.9845A and c=5.8897A.The structure contains facesharing octahedral CrAs6 chains along the c-axis,which are arranged triangularly in the ab-plane and separated by a significantly large distance of 8.9845A.The magnetic properties,resistivity and specific heat measurements were performed.La3CrAs5 exhibits a metallic state with Fermi liquid behavior at low temperatures and undergoes a ferromagnetic transition at Curie temperature TC^50 K.First-principles theoretical studies were conducted to calculate its band structure and density of states(DOS),which indicated that the non-negligible contribution of La to the DOS near the Fermi level caused La3CrAs5 to be a three-dimensional(3D)metal.The crystal orbital Hamilton population(-COHP)was also calculated to explain the global stability and bonding characteristics in the structure of La3CrAs5.展开更多
基金Project supported by the National Key R&D Program of China(Grant No.2017YFB0405703)the Ministry of Science and Technology of China(Grant Nos.2018YFA03057001 and 2015CB921000)the National Natural Science Foundation of China through the Research Projects(Grant Nos.11534016and 61504166)
文摘Chemical pressure induced by iso-valent doping has been widely employed to tune physical properties of materials. In this work, we report effects of chemical pressure by substitution of Sb or P into As on a recently discovered diluted magnetic semiconductor(Ba,K)(Zn,Mn)_2 As_2, which has the record of reliable Curie temperature of 230 K due to independent charge and spin doping. Sb and P are substituted into As-site to produce negative and positive chemical pressures, respectively.X-ray diffraction results demonstrate the successful chemical solution of dopants. Magnetic properties of both K-underdoped and K-optimal-doped samples are effectively tuned by Sb-and P-doping. The Hall effect measurements do not show decrease in carrier concentrations upon Sb-and P-doping. Impressively, magnetoresistance is significantly improved from7% to 27% by only 10% P-doping, successfully extending potential application of(Ba,K)(Zn,Mn)_2 As_2.
基金Project supported by the National Key R&D Program of China and the National Natural Science Foundation of China(Grant Nos.2018YFA0305700,2017YFA0302900,11974410,and 11534016)。
文摘A new compound with one-dimensional spin chains, Ba9Co3Se(15), was synthesized under high pressure and high temperature conditions and systematically characterized via structural, transport and magnetic measurements. Ba9Co3Se(15) crystallizes in a hexagonal structure with the space group P-6c2(No. 188) and lattice constants of a = b = 9.6765 ? and c = 18.9562 ?. The structure consists of trimeric face-sharing octahedral CoSe6 chains, which are arranged in a triangular lattice in the ab-plane and separated by Ba atoms. The distance of the nearest neighbor of CoSe6 chains is very large, given by the lattice constant a = 9.6765 ?. The Weiss temperature Tθ associated with the intra-chain coupling strength is about -346 K. However, no long-range magnetic order but a spin glass transition at ~ 3 K has been observed. Our results indicate that the spin glass behavior in Ba9Co3Se(15) mainly arises from the magnetic frustration due to the geometrically frustrated triangular lattice.
基金supported by the Doctoral Fund of Henan University of Technology(Grant No.2020BS029)the National Key R&D Program of China(Grant Nos.2018YFA0305700 and 2017YFA0302900)+1 种基金the National Natural Science Foundation of China(Grant Nos.11974410 and 11820101003)the Stable Support Plan Program of Shenzhen Natural Science Fund(Grant No.20200925152415003)。
文摘A series of samples of Ba_(9)Co_(3)(Se_(1−x)S_(x))_(15)(x=0,0.05,0.1,0.15,0.2)with quasi-one-dimensional(1D)structure were successfully synthesized under high-temperature and high-pressure conditions.The influence of partial substitution of S for Se on the structure,electronic transport,and magnetic properties of Ba_(9)Co_(3)(Se_(1−x)S_(x))_(15) has been investigated in detail.The x-ray diffraction data shows that the lattice constant decreases linearly with increasing S-doping level,which follows the Vegrad’s law.The doped S atoms preferentially occupy the site of Se atoms in CoSe6 octahedron.Physical properties measurements indicate that all the samples of Ba_(9)Co_(3)(Se_(1−x)S_(x))_(15) are semiconducting and display spin glass behavior.As the replacement of Se by smaller size S,although the inter-chain distance decreases,the electronic hopping between CoSe/S6 chains is weakened and leads to an increase of band gap from 0.75 eV to 0.86 eV,since the S-3p electrons are more localized than Se-4p ones.Ba_(9)Co_(3)(Se_(1−x)S_(x))_(15) exhibits 1D conducting chain characteristic.
基金Supported by the National Natural Science Foundation of China(Grant Nos.U1930401,11974410,11820101003,11921004 and 11534016)the National Key R&D Program of China(Grant Nos.2018YFA0305703,2018YFA0305700 and 2017YFA0302900).
文摘Recently,a series of novel compounds Ba3MX5(M=Fe,Ti,V;X=Se,Te)with hexagonal crystal structures composed of quasi-1-dimensional(1D)magnetic chains has been synthesized by our research team using high-pressure and high-temperature methods.The initial hexagonal phases persist to the maximum achievable pressure,while spin configurations and magnetic interactions may change dramatically as a result of considerable reductions in interchain separations upon pressurization.These compounds therefore offer unique possibilities for studying the evolution of intrinsic electronic structures in quasi-1D magnetic systems.Here we present a systematic investigation of Ba9Fe3Te15,in which the interchain separations between trimerized 1D chains(~10.2Å)can be effectively modulated by external high pressure.The crystal structure especially along the 1D chains exhibits an abnormal expansion at^GPa,which accompanies trimerization entangled anomalous mixed-high-low spin transition.An insulator-metal transition has been observed under high pressure as a result of charge-transfer gap closing.Pressure-induced superconductivity emerges at 26 GPa,where the charge-transfer gap fully closes,3D electronic configuration forms and local spin fully collapses.
基金supported by the National Key R&D Program of China and the National Natural Science Foundation of China(2018YFA0305700,11974410,2017YFA0302900,2015CB921300,11534016 and 11974062)。
文摘In La-Cr-As system,the first ternary compound La3CrAs5 has been successfully synthesized under highpressure and high-temperature conditions.La3CrAs5 crystallizes into a hexagonal Hf5Sn3Cu-anti type structure with a space group of P63/mcm(No.193)and lattice parameters of a=b=8.9845A and c=5.8897A.The structure contains facesharing octahedral CrAs6 chains along the c-axis,which are arranged triangularly in the ab-plane and separated by a significantly large distance of 8.9845A.The magnetic properties,resistivity and specific heat measurements were performed.La3CrAs5 exhibits a metallic state with Fermi liquid behavior at low temperatures and undergoes a ferromagnetic transition at Curie temperature TC^50 K.First-principles theoretical studies were conducted to calculate its band structure and density of states(DOS),which indicated that the non-negligible contribution of La to the DOS near the Fermi level caused La3CrAs5 to be a three-dimensional(3D)metal.The crystal orbital Hamilton population(-COHP)was also calculated to explain the global stability and bonding characteristics in the structure of La3CrAs5.
