This paper examines an asymmetric spatiotemporal connection and climatic impact between the winter atmospheric blocking activity in the Euro-Atlantic sector and the life cycle of the North Atlantic Oscillation（NAO） ...This paper examines an asymmetric spatiotemporal connection and climatic impact between the winter atmospheric blocking activity in the Euro-Atlantic sector and the life cycle of the North Atlantic Oscillation（NAO） during the period 1950–2012. Results show that, for positive NAO（NAO＋） events, the instantaneous blocking（IB） frequency exhibits an enhancement along the southwest–northeast（SW–NE） direction from the eastern Atlantic to northeastern Europe（SW–NE pattern, hereafter）, which is particularly evident during the NAO＋decaying stage. By contrast, for negative NAO（NAO-）events, the IB frequency exhibits a spatially asymmetric southeast–northwest（SE–NW） distribution from central Europe to the North Atlantic and Greenland（SE–NW pattern, hereafter）. Moreover, for NAO-（NAO＋） events, the most marked decrease（increase） in the surface air temperature（SAT） in winter over northern Europe is in the decaying stage. For NAO＋events, the dominant positive temperature and precipitation anomalies exhibit the SW–NE-oriented distribution from western to northeastern Europe, which is parallel to the NAO＋-related blocking frequency distribution. For NAO-events, the dominant negative temperature anomaly is in northern and central Europe, whereas the dominant positive precipitation anomaly is distributed over southern Europe along the SW–NE direction. In addition, the downward infrared radiation controlled by the NAO＇s circulation plays a crucial role in the SAT anomaly distribution. It is further shown that the NAO＇s phase can act as an asymmetric impact on the European climate through producing this asymmetric spatiotemporal connection with the Euro-Atlantic IB frequency.展开更多
Using an effective field theory with correlations, magnetic properties of an octahedral chain described by a mixed spin Ising model are investigated. Unique phenomena such as multiple hysteresis loops, saturation magn...Using an effective field theory with correlations, magnetic properties of an octahedral chain described by a mixed spin Ising model are investigated. Unique phenomena such as multiple hysteresis loops, saturation magnetization, and reverse flip of the magnetization plateaus occur when certain typical parameters are applied. These results may be helpful to further investigate the magnetic properties of one-dimensional systems and could potentially be utilized in the design of spin devices.展开更多
A new single-molecule magnet [Mn11Fe1O12 （CH3COO）16（H2O）4]·2CH3COOH·4H2O （Mn11Fe1） has been synthesized. The structure has been studied by the single crystal x-ray diffraction. The difference of Jahn-T...A new single-molecule magnet [Mn11Fe1O12 （CH3COO）16（H2O）4]·2CH3COOH·4H2O （Mn11Fe1） has been synthesized. The structure has been studied by the single crystal x-ray diffraction. The difference of Jahn-Teller distortion between Fe^3＋ and Mn^3＋ ion reveals that Fe^3＋ ion substitutes for Mn^3＋ ion on the Mn（3） sites in the Mn12 skeleton. The temperature dependence of the magnetization gives a blocking temperature TB=1.9K for Mn11Fe1. Based on the magnetization process analysis of the crystal at T=2K, we suggest that Mn11Fe1 has the ground state with a total spin S=11/2.展开更多
Cold air outbreaks（CAOs）always hit East Asia during boreal winter and have significant impacts on human health and public transport.The amplitude and route of CAOs are closely associated with blocking circulations o...Cold air outbreaks（CAOs）always hit East Asia during boreal winter and have significant impacts on human health and public transport.The amplitude and route of CAOs are closely associated with blocking circulations over the Eurasian continent.Two categories of CAOs are recognized,namely,the ordinary cold wave events（CWEs）and the extensive and persistent extreme cold events（EPECEs）,with the latter having even stronger impacts.The blocking features associated with these two types of CAOs and their differences are investigated in this study on the intraseasonal timescale.What these two CAOs do have in common is that they are both preceded by the intensification and recurrence of a blocking high over the midlatitude North Atlantic.The difference between these events is primarily reflected on the spatial scale and duration of the corresponding blocking high.During the CWEs,blocking occurs around the Ural Mountains,and exhibits a regional feature.The resulting cold air temperature persists for only up to 8 days.In contrast,during the EPECEs,the blocking region is quite extensive and is not only confined around the Ural Mountains but also extends eastward into Northeast Asia in a southwest–northeast orientation.As a result,the cold air tends to accumulate over a large area and persists for a much longer time.The blocking activity is primarily induced by an increased frequency and eastward extension of the synoptic anticyclonic Rossby wave breaking（AWB）.Compared with the CWEs,characterized by a regional and short-lived synoptic AWB frequency,the EPE-CEs tend to be accompanied by more recurrent and eastward extensions of the synoptic AWB.展开更多
Many sandwich-type lanthanide complexes show extremely high energy barriers(Ueff)for the reversal of magnetization and high blocking temperatures,being the star molecules in the research area of single-molecule magnet...Many sandwich-type lanthanide complexes show extremely high energy barriers(Ueff)for the reversal of magnetization and high blocking temperatures,being the star molecules in the research area of single-molecule magnets.Herein,the preparation,structural determination,and magnetic property studies of two ansa-bridged Er-COT(COT=cyclooctatetraenyl dianion)complexes[KDME_(2)][Er((η^(8)-COT-Si^(Me2))_(2)O)](1)and[KDME_(2)][Er((η^(8)-COT-Si^(iPr2))_(2)O)]K[Er((η^(8)-COT-Si^(iPr2))_(2)O)](2)were reported.The Er(Ⅲ)ions in both complexes are sandwiched by two COT rings which are ansa-bridged by a[Si-O-Si]group.Magnetic studies reveal both complexes display slow magnetic relaxations with comparable energy barriers(228(5)K for 1,and 196(4)K for 2)and blocking temperatures(10.5 K for both complexes).The difference in the relaxation times(τ)for the two complexes was studied in details:different molecular vibrations induced by the substituents are the main reason forτfor 1 being about 10 times longer than for 2 at the same temperature above 10 K,while the quantum tunnelling of magnetization relaxation time(τQTM)for 2 is about 10 times longer than for 1 below 8 K,probably owing to the different dipolar interactions.Further rearrangement of molecular network with such ansa-bridged SMMs is promising to design molecular magnetic materials with enhanced properties or new properties.展开更多
An orthogonal coupling structure of NiO/CoPt/Pt/glass with perpendicular exchange bias effect has been prepared.The exchange bias is found to be strongly dependent on the interface roughness between NiO and CoPt layer...An orthogonal coupling structure of NiO/CoPt/Pt/glass with perpendicular exchange bias effect has been prepared.The exchange bias is found to be strongly dependent on the interface roughness between NiO and CoPt layer.The conventional inverse proportionality of the exchange bias field with the ferromagnetic thickness is not applicable to this top-pinned stacking structure.Moreover,an anomalous ferromagnetic thickness dependence of blocking temperature is also observed.A simulation on the basis of a spin configuration model with defects at the interface agrees well with the experimental observations.These findings suggest considerable contribution of the interface roughness to the perpendicular exchange bias.展开更多
基金support from the National Natural Science Foundation of China (Grant Nos. 41505075 and 41790473)the National Key Research and Development Program of China (Grant No. 2016YFA0601802)
文摘This paper examines an asymmetric spatiotemporal connection and climatic impact between the winter atmospheric blocking activity in the Euro-Atlantic sector and the life cycle of the North Atlantic Oscillation（NAO） during the period 1950–2012. Results show that, for positive NAO（NAO＋） events, the instantaneous blocking（IB） frequency exhibits an enhancement along the southwest–northeast（SW–NE） direction from the eastern Atlantic to northeastern Europe（SW–NE pattern, hereafter）, which is particularly evident during the NAO＋decaying stage. By contrast, for negative NAO（NAO-）events, the IB frequency exhibits a spatially asymmetric southeast–northwest（SE–NW） distribution from central Europe to the North Atlantic and Greenland（SE–NW pattern, hereafter）. Moreover, for NAO-（NAO＋） events, the most marked decrease（increase） in the surface air temperature（SAT） in winter over northern Europe is in the decaying stage. For NAO＋events, the dominant positive temperature and precipitation anomalies exhibit the SW–NE-oriented distribution from western to northeastern Europe, which is parallel to the NAO＋-related blocking frequency distribution. For NAO-events, the dominant negative temperature anomaly is in northern and central Europe, whereas the dominant positive precipitation anomaly is distributed over southern Europe along the SW–NE direction. In addition, the downward infrared radiation controlled by the NAO＇s circulation plays a crucial role in the SAT anomaly distribution. It is further shown that the NAO＇s phase can act as an asymmetric impact on the European climate through producing this asymmetric spatiotemporal connection with the Euro-Atlantic IB frequency.
基金Project supported by National Natural Science Foundation of China(Grant No.51920105011)the Key R&D Program of Liaoning Province of China(Grant No.2020JH2/10300079)。
文摘Using an effective field theory with correlations, magnetic properties of an octahedral chain described by a mixed spin Ising model are investigated. Unique phenomena such as multiple hysteresis loops, saturation magnetization, and reverse flip of the magnetization plateaus occur when certain typical parameters are applied. These results may be helpful to further investigate the magnetic properties of one-dimensional systems and could potentially be utilized in the design of spin devices.
基金Project supported by the National Natural Science Foundation of China （Grant No 10375088）.
文摘A new single-molecule magnet [Mn11Fe1O12 （CH3COO）16（H2O）4]·2CH3COOH·4H2O （Mn11Fe1） has been synthesized. The structure has been studied by the single crystal x-ray diffraction. The difference of Jahn-Teller distortion between Fe^3＋ and Mn^3＋ ion reveals that Fe^3＋ ion substitutes for Mn^3＋ ion on the Mn（3） sites in the Mn12 skeleton. The temperature dependence of the magnetization gives a blocking temperature TB=1.9K for Mn11Fe1. Based on the magnetization process analysis of the crystal at T=2K, we suggest that Mn11Fe1 has the ground state with a total spin S=11/2.
基金Supported by the National Natural Science Foundation of China(41305047,41375064,and 41630424)National Science and Technology Support Program of China(2015BAC03B03)
文摘Cold air outbreaks（CAOs）always hit East Asia during boreal winter and have significant impacts on human health and public transport.The amplitude and route of CAOs are closely associated with blocking circulations over the Eurasian continent.Two categories of CAOs are recognized,namely,the ordinary cold wave events（CWEs）and the extensive and persistent extreme cold events（EPECEs）,with the latter having even stronger impacts.The blocking features associated with these two types of CAOs and their differences are investigated in this study on the intraseasonal timescale.What these two CAOs do have in common is that they are both preceded by the intensification and recurrence of a blocking high over the midlatitude North Atlantic.The difference between these events is primarily reflected on the spatial scale and duration of the corresponding blocking high.During the CWEs,blocking occurs around the Ural Mountains,and exhibits a regional feature.The resulting cold air temperature persists for only up to 8 days.In contrast,during the EPECEs,the blocking region is quite extensive and is not only confined around the Ural Mountains but also extends eastward into Northeast Asia in a southwest–northeast orientation.As a result,the cold air tends to accumulate over a large area and persists for a much longer time.The blocking activity is primarily induced by an increased frequency and eastward extension of the synoptic anticyclonic Rossby wave breaking（AWB）.Compared with the CWEs,characterized by a regional and short-lived synoptic AWB frequency,the EPE-CEs tend to be accompanied by more recurrent and eastward extensions of the synoptic AWB.
基金supported by the National Natural Science Foundation of China(92261203,22101116,and 21971106)Key Laboratory of Rare Earth Chemistry of Guangdong Higher Education Institutes(2022KSYS006)+1 种基金the Stable Support Plan Program of Shenzhen Natural Science Fund(20200925161141006)Shenzhen Fundamental Research Program(JCYJ20220530115001002 and JCYJ20220818100417037).
文摘Many sandwich-type lanthanide complexes show extremely high energy barriers(Ueff)for the reversal of magnetization and high blocking temperatures,being the star molecules in the research area of single-molecule magnets.Herein,the preparation,structural determination,and magnetic property studies of two ansa-bridged Er-COT(COT=cyclooctatetraenyl dianion)complexes[KDME_(2)][Er((η^(8)-COT-Si^(Me2))_(2)O)](1)and[KDME_(2)][Er((η^(8)-COT-Si^(iPr2))_(2)O)]K[Er((η^(8)-COT-Si^(iPr2))_(2)O)](2)were reported.The Er(Ⅲ)ions in both complexes are sandwiched by two COT rings which are ansa-bridged by a[Si-O-Si]group.Magnetic studies reveal both complexes display slow magnetic relaxations with comparable energy barriers(228(5)K for 1,and 196(4)K for 2)and blocking temperatures(10.5 K for both complexes).The difference in the relaxation times(τ)for the two complexes was studied in details:different molecular vibrations induced by the substituents are the main reason forτfor 1 being about 10 times longer than for 2 at the same temperature above 10 K,while the quantum tunnelling of magnetization relaxation time(τQTM)for 2 is about 10 times longer than for 1 below 8 K,probably owing to the different dipolar interactions.Further rearrangement of molecular network with such ansa-bridged SMMs is promising to design molecular magnetic materials with enhanced properties or new properties.
文摘An orthogonal coupling structure of NiO/CoPt/Pt/glass with perpendicular exchange bias effect has been prepared.The exchange bias is found to be strongly dependent on the interface roughness between NiO and CoPt layer.The conventional inverse proportionality of the exchange bias field with the ferromagnetic thickness is not applicable to this top-pinned stacking structure.Moreover,an anomalous ferromagnetic thickness dependence of blocking temperature is also observed.A simulation on the basis of a spin configuration model with defects at the interface agrees well with the experimental observations.These findings suggest considerable contribution of the interface roughness to the perpendicular exchange bias.
