The anharmonicity of lattice vibration is mainly responsible for the coefficient of thermal expansion(CTE)of materials.External stimuli,such as magnetic and electric fields,thus cannot effectively change the CTE,much ...The anharmonicity of lattice vibration is mainly responsible for the coefficient of thermal expansion(CTE)of materials.External stimuli,such as magnetic and electric fields,thus cannot effectively change the CTE,much less the sign variation from positive to negative or vice versa.In this study,we report significant magnetic field effects on the CTE of zircon-and scheelite-type DyCrO_(4) prepared at ambient and high pressures,respectively.At zero field,the zircon-type DyCrO_(4) exhibits a negative CTE below the ferromagnetic-order temperature of 23 K.With increasing field up to≥1.0 T,however,the sign of the CTE changes from negative to positive.In the scheelite phase,magnetic field can change the initially positive CTE to be negative with a field up to 2.0 T,and then a reentrant positive CTE is induced by enhanced fields≥3.5 T.Both zircon and scheelite phases exhibit considerable magnetostrictive effects with the absolute values as high as~800 ppm at 2 K and 10 T.The strong spin–lattice coupling is discussed to understand the unprecedented sign changes of the CTE caused by applying magnetic fields.The current DyCrO_(4) provides the first example of field-induced sign change of thermal expansion,opening up a way to readily control the thermal expansion beyond the conventional chemical substitution.展开更多
We report the synthesis and characterization of a single-molecule magnet composed of triangular clusters of dysprosium ions.The structural study shows that the symmetry changes from one polar point group(mm2)at room t...We report the synthesis and characterization of a single-molecule magnet composed of triangular clusters of dysprosium ions.The structural study shows that the symmetry changes from one polar point group(mm2)at room temperature to another polar point group(m)at low temperature.Magnetic studies and theory calculations illustrate that the vortex distribution of magnetic dipoles in the triangular dysprosium clusters forms a toroidal magnetic moment.Interestingly,the analysis of AC magnetic susceptibility reveals the coexistence of three distinct magnetic relaxation processes,corresponding to the Raman,Orbach,and QTM relaxation pathways,respectively.The sum of three modified Debye functions is successfully used to describe the multiple relaxation behavior.展开更多
基金the National Key R&D Program of China(Grant Nos.2021YFA1400300 and 2018YFA0305700)the National Natural Science Foundation of China(Grant Nos.11934017,12261131499,51725104,11921004,11904392,and 22271309)+1 种基金the Beijing Natural Science Foundation(Grant No.Z200007)the Chinese Academy of Sciences(Grant No.XDB33000000)。
文摘The anharmonicity of lattice vibration is mainly responsible for the coefficient of thermal expansion(CTE)of materials.External stimuli,such as magnetic and electric fields,thus cannot effectively change the CTE,much less the sign variation from positive to negative or vice versa.In this study,we report significant magnetic field effects on the CTE of zircon-and scheelite-type DyCrO_(4) prepared at ambient and high pressures,respectively.At zero field,the zircon-type DyCrO_(4) exhibits a negative CTE below the ferromagnetic-order temperature of 23 K.With increasing field up to≥1.0 T,however,the sign of the CTE changes from negative to positive.In the scheelite phase,magnetic field can change the initially positive CTE to be negative with a field up to 2.0 T,and then a reentrant positive CTE is induced by enhanced fields≥3.5 T.Both zircon and scheelite phases exhibit considerable magnetostrictive effects with the absolute values as high as~800 ppm at 2 K and 10 T.The strong spin–lattice coupling is discussed to understand the unprecedented sign changes of the CTE caused by applying magnetic fields.The current DyCrO_(4) provides the first example of field-induced sign change of thermal expansion,opening up a way to readily control the thermal expansion beyond the conventional chemical substitution.
基金Project supported by the National Key Research and Development Program of China(Grant No.2021YFA1400303)the National Natural Science Foundation of China(Grant No.12227806)。
文摘We report the synthesis and characterization of a single-molecule magnet composed of triangular clusters of dysprosium ions.The structural study shows that the symmetry changes from one polar point group(mm2)at room temperature to another polar point group(m)at low temperature.Magnetic studies and theory calculations illustrate that the vortex distribution of magnetic dipoles in the triangular dysprosium clusters forms a toroidal magnetic moment.Interestingly,the analysis of AC magnetic susceptibility reveals the coexistence of three distinct magnetic relaxation processes,corresponding to the Raman,Orbach,and QTM relaxation pathways,respectively.The sum of three modified Debye functions is successfully used to describe the multiple relaxation behavior.
