Due to the lack of inversion,mirror or other roto-inversion symmetries,chiral crystals possess a well-defined handedness which,when combined with time-reversal symmetry breaking from the application of magnetic fields...Due to the lack of inversion,mirror or other roto-inversion symmetries,chiral crystals possess a well-defined handedness which,when combined with time-reversal symmetry breaking from the application of magnetic fields,can give rise to directional dichroism of the electrical transport phenomena via the magnetochiral anisotropy.In this study,we investigate the nonreciprocal magneto-transport in microdevices of NbGe_(2),a superconductor with structural chirality.A giant nonreciprocal signal from vortex motions is observed during the superconducting transition,with the ratio of nonreciprocal resistance to the normal resistanceγreaching 6×10^(5)T^(-1)·A^(-1).Interestingly,the intensity can be adjusted and even sign-reversed by varying the current,the temperature,and the crystalline orientation.Our findings illustrate intricate vortex dynamics and offer ways of manipulation on the rectification effect in superconductors with structural chirality.展开更多
Kagome magnets have attracted considerable research attention due to the interplay between topology,magnetism and electronic correlations.In this study we report single-crystal synthesis of a series of the kagome magn...Kagome magnets have attracted considerable research attention due to the interplay between topology,magnetism and electronic correlations.In this study we report single-crystal synthesis of a series of the kagome magnets.RCr_(6)Ge_(6)(R=Gd-Tm) that possess defect-free Cr kagome lattices and systematically study their magnetic and electrical transport properties.The transition from a canted ferrimagnetic to a paramagnetic state in GdCr_(6)Ge_(6),TbCr_(6)Ge_(6),DyCr_(6)Ge_(6),HoCr_(6)Ge_(6),ErCr_(6)Ge_(6) and TmCr_(6)Ge_(6) occurs at 11.3 K,10.8 K,4.3 K,2.5 K,3.3 K and below 2 K,respectively,due to R-R interactions within the compounds.Magnetization measurements reveal highly anisotropic magnetism with canted magnetic moments in these compounds.In electrical transport,both negative and positive magnetoresistances at different magnetic fields and temperatures have been observed due to the competition between different scattering mechanisms.This work enriches our understanding of the Cr-based kagome magnets and paves the way to search for possible topological responses in this family.展开更多
The discovery of Dirac semimetal and Weyl semimetal has motivated a growing passion for investigating the unique magneto-transport properties in the topological materials.A Weyl semimetal can host Weyl fermions as its...The discovery of Dirac semimetal and Weyl semimetal has motivated a growing passion for investigating the unique magneto-transport properties in the topological materials.A Weyl semimetal can host Weyl fermions as its low-energy quasi-particle excitations,and therefore perform exotic features analogous to those in high-energy physics,such as the violation of the chiral charge conservation known as the chiral anomaly.One of the electrical transport signatures of the chiral anomaly is the Adler-Bell-Jackiw（ABJ） anomaly which presents as a negative magnetoresistance when the magnetic field and the current are parallel.Very recently,numerous experiments reported negative longitudinal magnetoresistance（NLMR） in topological materials,but the details of the measurement results are various.Here the materials and the corresponding experiment results are briefly reviewed.Besides the plausible explanation of the ABJ anomaly,some other origins of the NLMR are also discussed.展开更多
We report magnetization and Raman spectroscopy study on single crystals of VOCl,a van der Waals antiferromagnetic material.Magnetization measurement confirms an antiferromagnetic transition at 79 K and a magnetic easy...We report magnetization and Raman spectroscopy study on single crystals of VOCl,a van der Waals antiferromagnetic material.Magnetization measurement confirms an antiferromagnetic transition at 79 K and a magnetic easy axis along crystallographic a direction.The temperature-dependent Raman spectrum reveals five peaks at 30 K.Below the Neel temperature TN,the Raman-active modes 247 cm^(−1) and 404 cm^(−1) remarkably deviate from the standard Boltzmann function,which is ascribed to the strong magnetoelastic coupling between spins and phonons.We further observe an anomaly in 383 cm^(−1) mode at around 150 K.This coincides with the broad maximum in VOCl’s magnetic susceptibility,suggesting a development of short-ranged magnetic order at this temperature.展开更多
We conducted a comparative study of the magnetic and transport properties of single-crystalline LaCo_(2)As_(2) and NdCo_(2)As_(2).LaCo_(2)As_(2) is a soft metallic ferromagnet which exhibits purely intrinsic anomalous...We conducted a comparative study of the magnetic and transport properties of single-crystalline LaCo_(2)As_(2) and NdCo_(2)As_(2).LaCo_(2)As_(2) is a soft metallic ferromagnet which exhibits purely intrinsic anomalous Hall effect(AHE) due to Co-3d electrons. With Nd-4f electronic magnetism, ferrimagnetic NdCo_(2)As_(2) manifests pronounced sign reversal and multiple hysteresis loops in temperature-and field-dependent magnetization, Hall resistivity, and magnetoresistance, due to complicated magnetic structural changes. We reveal that the AHE for NdCo_(2)As_(2) is stemming from the Co sub-lattice and deduce its phase diagram which includes magnetic compensation and two meta-magnetic phase transitions. The sensitivity of the Hall effect on the details of the magnetic structures in ferrimagnetic NdCo_(2)As_(2) provides a unique opportunity to explore the magnetic interaction between 4f and 3d electrons and its impact on the electronic structure.展开更多
Transition metal and rare earth intermetallics have been a fertile playground for research of various quantum states.We report detailed magnetic studies on Sm Mn_(2)Ge_(2),an anisotropic itinerant magnet with multiple...Transition metal and rare earth intermetallics have been a fertile playground for research of various quantum states.We report detailed magnetic studies on Sm Mn_(2)Ge_(2),an anisotropic itinerant magnet with multiple magnetic phases.The critical behavior of the ferromagnetic phase transition is investigated by employing the modified Arrott plot with the Kouvel-Fisher method.The critical temperature TCis determined to be around 342.7 K with critical exponents ofβ=0.417 andγ=1.122,and the interaction function is found to be J(r)~r^(-4.68),suggesting the coexistence of long-range and shortrange magnetic interactions.Our results contribute to the understanding of complex magnetism in Sm Mn_(2)Ge_(2),which may provide fundamental guidance in future spintronic applications.展开更多
Geometrical frustration in low-dimensional magnetic systems has been an intriguing research aspect,where the suppression of conventional magnetic order may lead to exotic ground states such as spin glass or spin liqui...Geometrical frustration in low-dimensional magnetic systems has been an intriguing research aspect,where the suppression of conventional magnetic order may lead to exotic ground states such as spin glass or spin liquid.In this work we report the synthesis and magnetism study of the monocrystalline Mn_(2)Ga_(2)S_(5),featuring both the van derWaals structure and a bilayered triangular Mn lattice.Magnetic susceptibility reveals a significant antiferromagnetic interaction with a Curie-Weiss temperature θ_(w)~-260 K and a high spin S=5/2 Mn^(2+) state.However,no long range magnetic order has been found down to 2 K,and a spin freezing transition is found to occur at around 12 K well below its θ_(w).This yields a frustration index of f=-θ_(w)/T_(f)≈22,an indication that the system is highly frustrated.The absence of a double-peak structure in magnetic specific heat compared with the TM_(2)S_(4) compounds implies that the spin freezing behavior in Mn_(2)Ga_(2)S_(5)is a result of the competition between exchange interactions and the 2D crystalline structure.Our results suggest that the layered Mn_(2)Ga_(2)S_(5)would be an excellent candidate for investigating the physics of 2D magnetism and spin disordered state.展开更多
基金Project supported by the National Key R&D Program of China(Grant No.2022YFA1403603)the National Natural Science Foundation of China(Grant Nos.U2032213,12104461,12374129,and 12304156)+1 种基金Chinese Academy of Sciences(Grant Nos.YSBR-084,and JZHKYPT-2021-08)A portion of this work was supported by the High Magnetic Field Laboratory of Anhui Province.
文摘Due to the lack of inversion,mirror or other roto-inversion symmetries,chiral crystals possess a well-defined handedness which,when combined with time-reversal symmetry breaking from the application of magnetic fields,can give rise to directional dichroism of the electrical transport phenomena via the magnetochiral anisotropy.In this study,we investigate the nonreciprocal magneto-transport in microdevices of NbGe_(2),a superconductor with structural chirality.A giant nonreciprocal signal from vortex motions is observed during the superconducting transition,with the ratio of nonreciprocal resistance to the normal resistanceγreaching 6×10^(5)T^(-1)·A^(-1).Interestingly,the intensity can be adjusted and even sign-reversed by varying the current,the temperature,and the crystalline orientation.Our findings illustrate intricate vortex dynamics and offer ways of manipulation on the rectification effect in superconductors with structural chirality.
基金Project supported by the National Key R&D Program of China(Grant No.2021YFA1600204)the National Natural Science Foundation of China(Grant Nos.U2032213,12104461,12374129,12304156,and 52325105)+1 种基金Chinese Academy of Sciences(Grant Nos.YSBR-084 and JZHKYPT2021-08)supported by the High Magnetic Field Laboratory of Anhui Province。
文摘Kagome magnets have attracted considerable research attention due to the interplay between topology,magnetism and electronic correlations.In this study we report single-crystal synthesis of a series of the kagome magnets.RCr_(6)Ge_(6)(R=Gd-Tm) that possess defect-free Cr kagome lattices and systematically study their magnetic and electrical transport properties.The transition from a canted ferrimagnetic to a paramagnetic state in GdCr_(6)Ge_(6),TbCr_(6)Ge_(6),DyCr_(6)Ge_(6),HoCr_(6)Ge_(6),ErCr_(6)Ge_(6) and TmCr_(6)Ge_(6) occurs at 11.3 K,10.8 K,4.3 K,2.5 K,3.3 K and below 2 K,respectively,due to R-R interactions within the compounds.Magnetization measurements reveal highly anisotropic magnetism with canted magnetic moments in these compounds.In electrical transport,both negative and positive magnetoresistances at different magnetic fields and temperatures have been observed due to the competition between different scattering mechanisms.This work enriches our understanding of the Cr-based kagome magnets and paves the way to search for possible topological responses in this family.
基金Project supported by the National Basic Research Program of China(Grant Nos.2013CB921901 and 2014CB239302)
文摘The discovery of Dirac semimetal and Weyl semimetal has motivated a growing passion for investigating the unique magneto-transport properties in the topological materials.A Weyl semimetal can host Weyl fermions as its low-energy quasi-particle excitations,and therefore perform exotic features analogous to those in high-energy physics,such as the violation of the chiral charge conservation known as the chiral anomaly.One of the electrical transport signatures of the chiral anomaly is the Adler-Bell-Jackiw（ABJ） anomaly which presents as a negative magnetoresistance when the magnetic field and the current are parallel.Very recently,numerous experiments reported negative longitudinal magnetoresistance（NLMR） in topological materials,but the details of the measurement results are various.Here the materials and the corresponding experiment results are briefly reviewed.Besides the plausible explanation of the ABJ anomaly,some other origins of the NLMR are also discussed.
基金supported by the National Natural Science Foundation of China(Grant Nos.U2032213,U1832214,and 11774352)。
文摘We report magnetization and Raman spectroscopy study on single crystals of VOCl,a van der Waals antiferromagnetic material.Magnetization measurement confirms an antiferromagnetic transition at 79 K and a magnetic easy axis along crystallographic a direction.The temperature-dependent Raman spectrum reveals five peaks at 30 K.Below the Neel temperature TN,the Raman-active modes 247 cm^(−1) and 404 cm^(−1) remarkably deviate from the standard Boltzmann function,which is ascribed to the strong magnetoelastic coupling between spins and phonons.We further observe an anomaly in 383 cm^(−1) mode at around 150 K.This coincides with the broad maximum in VOCl’s magnetic susceptibility,suggesting a development of short-ranged magnetic order at this temperature.
基金Project supported by the National Key Research and Development Program of China(Grant No.2018YFB1502502)the National Natural Science Foundation of China(Grant Nos.12141002 and 12225401)+6 种基金the Fund from Foshan Xianhu Laboratory of the Advanced Energy Science and Technology Guangdong Laboratorysupported by the Interdisciplinary Program of Wuhan National High Magnetic Field Center(Grant No.WHMFC202123)Huazhong University of Science and Technologysupported by the National Natural Science Foundation of China(Grant Nos.12074041 and 11674030)the Foundation of the National Key Laboratory of Shock Wave and Detonation Physics(Grant No.6142A03191005)the National Key Research and Development Program of China(Grant No.2016YFA0302300)the startup funding of Beijing Normal University。
文摘We conducted a comparative study of the magnetic and transport properties of single-crystalline LaCo_(2)As_(2) and NdCo_(2)As_(2).LaCo_(2)As_(2) is a soft metallic ferromagnet which exhibits purely intrinsic anomalous Hall effect(AHE) due to Co-3d electrons. With Nd-4f electronic magnetism, ferrimagnetic NdCo_(2)As_(2) manifests pronounced sign reversal and multiple hysteresis loops in temperature-and field-dependent magnetization, Hall resistivity, and magnetoresistance, due to complicated magnetic structural changes. We reveal that the AHE for NdCo_(2)As_(2) is stemming from the Co sub-lattice and deduce its phase diagram which includes magnetic compensation and two meta-magnetic phase transitions. The sensitivity of the Hall effect on the details of the magnetic structures in ferrimagnetic NdCo_(2)As_(2) provides a unique opportunity to explore the magnetic interaction between 4f and 3d electrons and its impact on the electronic structure.
基金supported by the National Key Research and Development Program of China(Grant No.2021YFA1600204)the Innovation Program for Quantum Science and Technology(Grant No.2021ZD0302802)+2 种基金the National Natural Science Foundation of China(Grant Nos.U1832214,U2032213,12104461,and 12074135)the High Magnetic Field Laboratory of Anhuisupported by the Start-up Project of Anhui University(Grant No.S020318001/020)。
文摘Transition metal and rare earth intermetallics have been a fertile playground for research of various quantum states.We report detailed magnetic studies on Sm Mn_(2)Ge_(2),an anisotropic itinerant magnet with multiple magnetic phases.The critical behavior of the ferromagnetic phase transition is investigated by employing the modified Arrott plot with the Kouvel-Fisher method.The critical temperature TCis determined to be around 342.7 K with critical exponents ofβ=0.417 andγ=1.122,and the interaction function is found to be J(r)~r^(-4.68),suggesting the coexistence of long-range and shortrange magnetic interactions.Our results contribute to the understanding of complex magnetism in Sm Mn_(2)Ge_(2),which may provide fundamental guidance in future spintronic applications.
基金supported by the National Natural Science Foundation of China(Grant Nos.U1832214,11774007,U2032213,and 12104461).
文摘Geometrical frustration in low-dimensional magnetic systems has been an intriguing research aspect,where the suppression of conventional magnetic order may lead to exotic ground states such as spin glass or spin liquid.In this work we report the synthesis and magnetism study of the monocrystalline Mn_(2)Ga_(2)S_(5),featuring both the van derWaals structure and a bilayered triangular Mn lattice.Magnetic susceptibility reveals a significant antiferromagnetic interaction with a Curie-Weiss temperature θ_(w)~-260 K and a high spin S=5/2 Mn^(2+) state.However,no long range magnetic order has been found down to 2 K,and a spin freezing transition is found to occur at around 12 K well below its θ_(w).This yields a frustration index of f=-θ_(w)/T_(f)≈22,an indication that the system is highly frustrated.The absence of a double-peak structure in magnetic specific heat compared with the TM_(2)S_(4) compounds implies that the spin freezing behavior in Mn_(2)Ga_(2)S_(5)is a result of the competition between exchange interactions and the 2D crystalline structure.Our results suggest that the layered Mn_(2)Ga_(2)S_(5)would be an excellent candidate for investigating the physics of 2D magnetism and spin disordered state.
