Antiperovskite compounds Mn3Ag1-xCoxN （x =0.2, 0.5 and 0.8） are synthesized and the doping effect of the magnetic element Co at the Ag site is investigated. The crystal structure is not changed by the introduction o...Antiperovskite compounds Mn3Ag1-xCoxN （x =0.2, 0.5 and 0.8） are synthesized and the doping effect of the magnetic element Co at the Ag site is investigated. The crystal structure is not changed by the introduction of Co. However, with the increase of the content of Co, the spin reorientation gradually disappears and the antiferromagnetic transition changes to the ferromagnetic transition at the elevated temperature when x = 0.8. In addition, all of the magnetic phase transitions at the elevated temperature are always accompanied by the abnormal thermal expansion behaviors and an entropy change. Moreover, when x = 0.8, the coefficient of linear expansion is -1.89 × 10^-6 K^-1 （290-310K, △T =20 K）, which is generally considered as the low thermal expansion.展开更多
We synthesize a series of Mn substituted （Li, Fe）OHFeSe superconductor single crystals via a modified ion-exchange method, with the Mn concentration z （the atomic ratio of Mn：Se） ranging from 0 to 0.07. The distr...We synthesize a series of Mn substituted （Li, Fe）OHFeSe superconductor single crystals via a modified ion-exchange method, with the Mn concentration z （the atomic ratio of Mn：Se） ranging from 0 to 0.07. The distribution homogeneity of the Mn element incorporated into the lattice of （Li, Fe）OHFeSe is checked by combined measurements of high-angle- annular-dark-field （HAADF） imaging and electron energy-loss spectroscopy （EELS）. Interestingly, we find that the superconducting transition temperature Tc and unit cell parameter c of the Mn-doped （Li, Fe）OHFeSe samples display similar V-shaped evolutions with the increasing dopant concentration z. We propose that, with increasing doping level, the Mn dopant first occupies the tetrahedral sites in the （Li, Fe）OH layers before starting to substitute the Fe element in the su- perconducting FeSe layers, which accounts for the V-shaped change in cell parameter c. The observed positive correlation between the Tc and lattice parameter c, regardless of the Mn doping level z, indicates that a larger interlayer separation, or a weaker interlayer coupling, is essential for the high-Tc superconductivity in （Li, Fe）OHFeSe. This agrees with our previous observations on powder, single crystal, and film samples of （Li, Fe）OHFeSe superconductors.展开更多
基金Supported by the National Natural Science Foundation of China under Grant No 51172012the Fundamental Research Funds for the Central Universities
文摘Antiperovskite compounds Mn3Ag1-xCoxN （x =0.2, 0.5 and 0.8） are synthesized and the doping effect of the magnetic element Co at the Ag site is investigated. The crystal structure is not changed by the introduction of Co. However, with the increase of the content of Co, the spin reorientation gradually disappears and the antiferromagnetic transition changes to the ferromagnetic transition at the elevated temperature when x = 0.8. In addition, all of the magnetic phase transitions at the elevated temperature are always accompanied by the abnormal thermal expansion behaviors and an entropy change. Moreover, when x = 0.8, the coefficient of linear expansion is -1.89 × 10^-6 K^-1 （290-310K, △T =20 K）, which is generally considered as the low thermal expansion.
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2017YFA0303003 and 2016YFA0300300)the National Natural Science Foundation of China(Grant No.11574370)the Strategic Priority Research Program and Key Research Program of Frontier Sciences of the Chinese Academy of Sciences(Grant Nos.QYZDY-SSW-SLH001,QYZDY-SSW-SLH008,and XDB07020100)
文摘We synthesize a series of Mn substituted （Li, Fe）OHFeSe superconductor single crystals via a modified ion-exchange method, with the Mn concentration z （the atomic ratio of Mn：Se） ranging from 0 to 0.07. The distribution homogeneity of the Mn element incorporated into the lattice of （Li, Fe）OHFeSe is checked by combined measurements of high-angle- annular-dark-field （HAADF） imaging and electron energy-loss spectroscopy （EELS）. Interestingly, we find that the superconducting transition temperature Tc and unit cell parameter c of the Mn-doped （Li, Fe）OHFeSe samples display similar V-shaped evolutions with the increasing dopant concentration z. We propose that, with increasing doping level, the Mn dopant first occupies the tetrahedral sites in the （Li, Fe）OH layers before starting to substitute the Fe element in the su- perconducting FeSe layers, which accounts for the V-shaped change in cell parameter c. The observed positive correlation between the Tc and lattice parameter c, regardless of the Mn doping level z, indicates that a larger interlayer separation, or a weaker interlayer coupling, is essential for the high-Tc superconductivity in （Li, Fe）OHFeSe. This agrees with our previous observations on powder, single crystal, and film samples of （Li, Fe）OHFeSe superconductors.
