Nematic order and its fluctuations have been widely found in iron-based superconductors. Above the nematic order transition temperature, the resistivity shows a linear relationship with the uniaxial pressure or strain...Nematic order and its fluctuations have been widely found in iron-based superconductors. Above the nematic order transition temperature, the resistivity shows a linear relationship with the uniaxial pressure or strain along the nematic direction and the normalized slope is thought to be associated with nematic susceptibility. Here we systematically studied the uniaxial pressure dependence of the resistivity in Sr1 _xBaxFel.97Nio.03As2, where nonlinear behaviors are observed near the nematic transition temperature. We show that it can be well explained by the Landau theory for the second-order phase transitions considering that the external field is not zero. The effect of the coupling between the isotropic and nematic channels is shown to be negligible. Moreover, our results suggest that the nature of the magnetic and nematic transitions in Srl xBaxFe2As2 is determined by the strength of the magnetic-elastic coupling.展开更多
We use neutron powder diffraction to study the non-superconducting phases of ThFeAsN1-xOx with x = 0.15,0.6.In our previous results of the superconducting phase ThFeAsN with Tc = 30 K,no magnetic transition is observe...We use neutron powder diffraction to study the non-superconducting phases of ThFeAsN1-xOx with x = 0.15,0.6.In our previous results of the superconducting phase ThFeAsN with Tc = 30 K,no magnetic transition is observed by cooling down to 6 K,and possible oxygen occupancy at the nitrogen site is shown in the refinement[Europhys.Lett.117(2017)57005].Here in the oxygen doped system ThFeAsN1-xOx,two superconducting regions(0≤x≤0.1 and 0.25≤x≤0.55)are identified by transport experiments[J.Phys.:Condens.Matter30(2018)255602].However,within the resolution of our neutron powder diffraction experiment,neither the intermediate doping x= 0.15 nor the heavily overdoped compound x = 0.6 shows any magnetic order from 300 K to 4 K.Therefore,while it shares the common phenomenon of two superconducting domes as most 1111-type iron-based superconductors,the magneticall.y ordered parent compound may not exist in this nitride family.展开更多
We use neutron powder diffraction to investigate the magnetic and crystalline structure of Cr_(2)GaN.A magnetic phase transition is identified at T≈170 K,whereas no trace of structural transition is observed down to ...We use neutron powder diffraction to investigate the magnetic and crystalline structure of Cr_(2)GaN.A magnetic phase transition is identified at T≈170 K,whereas no trace of structural transition is observed down to 6 K.Combining Rietveld refinement with irreducible representations,the spin configuration of Cr ions in Cr_(2)GaN is depicted as an incommensurate sinusoidal modulated structure characterized by a propagating vector k=(0.365,0.365,0).Upon warming up to the paramagnetic state,the magnetic order parameter closely resembles to the temperature dependence of c-axis lattice parameter,suggesting strong magneto-elastic coupling in this compound.Therefore,Cr_(2)Ga N provides a potential platform for exploration of magnetically tuned properties such as magnetoelectric,magnetostrictive and magnetocaloric effects,as well as their applications.展开更多
基金Project supported by the Science Fonds from the Ministry of Science and Technology of China(Grant Nos.2017YFA0302903,017YFA0303103,2016YFA0300502,and 2015CB921302)the National Natural Science Foundation of China(Grant Nos.11674406 and 11674372)+1 种基金the“Strategic Priority Research Program(B)”of the Chinese Academy of Sciences(Grant Nos.XDB07020300 and XDB07020200)the Youth Innovation Promotion Association of the Chinese Academy of Sciences
文摘Nematic order and its fluctuations have been widely found in iron-based superconductors. Above the nematic order transition temperature, the resistivity shows a linear relationship with the uniaxial pressure or strain along the nematic direction and the normalized slope is thought to be associated with nematic susceptibility. Here we systematically studied the uniaxial pressure dependence of the resistivity in Sr1 _xBaxFel.97Nio.03As2, where nonlinear behaviors are observed near the nematic transition temperature. We show that it can be well explained by the Landau theory for the second-order phase transitions considering that the external field is not zero. The effect of the coupling between the isotropic and nematic channels is shown to be negligible. Moreover, our results suggest that the nature of the magnetic and nematic transitions in Srl xBaxFe2As2 is determined by the strength of the magnetic-elastic coupling.
基金Supported by the Strategic Priority Research Program of Chinese Academy of Sciences under Grant Nos XDB07020300and XDB25000000the National Key Research and Development Program of China under Grant Nos 2017YFA0303103,2017YFA0302903 and 2016YFA0300502+3 种基金the National Natural Science Foundation of China under Grant Nos 11374011,11504347,11304183,11674406 and 11822411the Youth Innovation Promotion Association of Chinese Academy of Sciences under Grant No2016004the Key Laboratory of Neutron Physics of CAEP under Grant No 2015AB03the Science Challenge Project under Grant No TZ2016004
文摘We use neutron powder diffraction to study the non-superconducting phases of ThFeAsN1-xOx with x = 0.15,0.6.In our previous results of the superconducting phase ThFeAsN with Tc = 30 K,no magnetic transition is observed by cooling down to 6 K,and possible oxygen occupancy at the nitrogen site is shown in the refinement[Europhys.Lett.117(2017)57005].Here in the oxygen doped system ThFeAsN1-xOx,two superconducting regions(0≤x≤0.1 and 0.25≤x≤0.55)are identified by transport experiments[J.Phys.:Condens.Matter30(2018)255602].However,within the resolution of our neutron powder diffraction experiment,neither the intermediate doping x= 0.15 nor the heavily overdoped compound x = 0.6 shows any magnetic order from 300 K to 4 K.Therefore,while it shares the common phenomenon of two superconducting domes as most 1111-type iron-based superconductors,the magneticall.y ordered parent compound may not exist in this nitride family.
基金supported by the National Natural Science Foundation of China(Grant Nos.11822411,12061130200,11961160699,11974392,and 52101236)the National Key Research and Development Program of China(Grant Nos.2018YFA0704200,2017YFA0303100,and 2020YFA0406003)+4 种基金the Strategic Priority Research Program(B)of the CAS(GrantNo.XDB25000000)K.C.Wong Education Foundation(Grant No.GJTD-2020-01)the Youth Innovation Promotion Association of the CAS(Grant No.Y202001)Beijing Natural Science Foundation(Grant No.JQ19002)the Newton Advanced Fellowship funding from the Royal Society of UK(Grant No.NAFR1201248)。
文摘We use neutron powder diffraction to investigate the magnetic and crystalline structure of Cr_(2)GaN.A magnetic phase transition is identified at T≈170 K,whereas no trace of structural transition is observed down to 6 K.Combining Rietveld refinement with irreducible representations,the spin configuration of Cr ions in Cr_(2)GaN is depicted as an incommensurate sinusoidal modulated structure characterized by a propagating vector k=(0.365,0.365,0).Upon warming up to the paramagnetic state,the magnetic order parameter closely resembles to the temperature dependence of c-axis lattice parameter,suggesting strong magneto-elastic coupling in this compound.Therefore,Cr_(2)Ga N provides a potential platform for exploration of magnetically tuned properties such as magnetoelectric,magnetostrictive and magnetocaloric effects,as well as their applications.