The Gaussian spin model with periodic interactions on the diamond-type hierarchical lattices is constructed by generalizing that with uniform interactions on translationally invariant lattices according to a class of ...The Gaussian spin model with periodic interactions on the diamond-type hierarchical lattices is constructed by generalizing that with uniform interactions on translationally invariant lattices according to a class of substitution sequences. The Gaussian distribution constants and imposed external magnetic fields are also periodic depending on the periodic characteristic of the interaction bonds. The critical behaviors of this generalized Gaussian model in external magnetic fields are studied by the exact renormalization-group approach and spin rescaling method. The critical points and all the critical exponents are obtained. The critical behaviors are found to be determined by the Gaussian distribution constants and the fractal dimensions of the lattices. When all the Gaussian distribution constants are the same, the dependence of the critical exponents on the dimensions of the lattices is the same as that of the Gaussian model with uniform interactions on translationally invariant lattices.展开更多
With the discovery of giant magnetoresistance(GMR),research effort has been made to exploiting the influence of spins on the mobility of electrons in ferromagnetic materials and/or artificial structures,which has lead...With the discovery of giant magnetoresistance(GMR),research effort has been made to exploiting the influence of spins on the mobility of electrons in ferromagnetic materials and/or artificial structures,which has lead to the idea of spintronics.A brief introduction is given to GMR effects from scientific background to experimental observations and theoretical models.In addition,the mechanisms of various magnetoresistance beyond the GMR are reviewed,for instance,tunnelling magnetoresistance,colossal magnetoresistance,and magnetoresistance in ferromagnetic semiconductors,nanowires,organic spintronics and non-magnetic systems.展开更多
Long-range magnetic orders in atomically thin ferromagnetic CrI3 trigger new fascinating physics and application perspectives.The physical properties of two-dimensional(2D)ferromagnetism CrI3 are significantly influen...Long-range magnetic orders in atomically thin ferromagnetic CrI3 trigger new fascinating physics and application perspectives.The physical properties of two-dimensional(2D)ferromagnetism CrI3 are significantly influenced by interlayer spacing and stacking order,which are sensitive to the hydrostatic pressure and external environments.However,there remains debate on the stacking order at low temperature.Here,we study the interlayer coupling and stacking order of non-encapsulated 2–5 layer and bulk CrI3 at 10 K by Raman spectroscopy;demonstrate a rhombohedral stacking in both antiferromagnetic and ferromagnetic CrI3.The opposite helicity dependence of Ag and Eg modes arising from phonon symmetry further validates the rhombohedral stacking.An anomalous temperature-dependent behavior is observed due to spin-phonon coupling below 60 K.Our study provides insights into the interlayer coupling and stacking orders of 2D ferromagnetic materials.展开更多
文摘The Gaussian spin model with periodic interactions on the diamond-type hierarchical lattices is constructed by generalizing that with uniform interactions on translationally invariant lattices according to a class of substitution sequences. The Gaussian distribution constants and imposed external magnetic fields are also periodic depending on the periodic characteristic of the interaction bonds. The critical behaviors of this generalized Gaussian model in external magnetic fields are studied by the exact renormalization-group approach and spin rescaling method. The critical points and all the critical exponents are obtained. The critical behaviors are found to be determined by the Gaussian distribution constants and the fractal dimensions of the lattices. When all the Gaussian distribution constants are the same, the dependence of the critical exponents on the dimensions of the lattices is the same as that of the Gaussian model with uniform interactions on translationally invariant lattices.
基金supported by the National Natural Science Foundation of China (Grant Nos. 51125004,10974120,B13029 and JQ200901)the National Basic Research Program of China (Grant Nos. 2013CB922303and 2009CB929202)
文摘With the discovery of giant magnetoresistance(GMR),research effort has been made to exploiting the influence of spins on the mobility of electrons in ferromagnetic materials and/or artificial structures,which has lead to the idea of spintronics.A brief introduction is given to GMR effects from scientific background to experimental observations and theoretical models.In addition,the mechanisms of various magnetoresistance beyond the GMR are reviewed,for instance,tunnelling magnetoresistance,colossal magnetoresistance,and magnetoresistance in ferromagnetic semiconductors,nanowires,organic spintronics and non-magnetic systems.
基金the financial support from the National Natural Science Foundation of China (51602040 and 51872039)the Science and Technology Program of Sichuan (M112018JY0025)the Scientific Research Foundation for New Teachers of UESTC (A03013023601007)
文摘Long-range magnetic orders in atomically thin ferromagnetic CrI3 trigger new fascinating physics and application perspectives.The physical properties of two-dimensional(2D)ferromagnetism CrI3 are significantly influenced by interlayer spacing and stacking order,which are sensitive to the hydrostatic pressure and external environments.However,there remains debate on the stacking order at low temperature.Here,we study the interlayer coupling and stacking order of non-encapsulated 2–5 layer and bulk CrI3 at 10 K by Raman spectroscopy;demonstrate a rhombohedral stacking in both antiferromagnetic and ferromagnetic CrI3.The opposite helicity dependence of Ag and Eg modes arising from phonon symmetry further validates the rhombohedral stacking.An anomalous temperature-dependent behavior is observed due to spin-phonon coupling below 60 K.Our study provides insights into the interlayer coupling and stacking orders of 2D ferromagnetic materials.
