The frequency in middle of magnon energy band in a five-layer ferromagnetic superlattice is studied byusing the linear spin-wave approach and Green's function technique.It is found that four energy gaps and corres...The frequency in middle of magnon energy band in a five-layer ferromagnetic superlattice is studied byusing the linear spin-wave approach and Green's function technique.It is found that four energy gaps and correspondingfour frequencie in middle of energy gaps exist in the magnon band along K_x direction perpendicular to the superlatticeplane.The spin quantum numbers and the interlayer exchange couplings all affect the four frequencies in middle of theenergy gaps.When all interlayer exchange couplings are same, the effect of spin quantum numbers on the frequency ω_(g1)in middle of the energy gap Δω_(12) is complicated, and the frequency ω_(g1) depends on the match of spin quantum numbersin each layer.Meanwhile, the frequencies ω_(g2), ω_(g3), and ω_(g4) in middle of other energy gaps increase monotonously withincreasing spin quantum numbers.When the spin quantum numbers in each layer are same, the frequencies ω_(g1), ω_(g2),ω_(g3), and ω_(g4) all increase monotonously with increasing interlayer exchange couplings.展开更多
The specific heats of both a two-layer ferromagnetic superlattice and a two-layer ferrimagnetic one arestudied.It is found that the spin quantum numbers,the interlayer and intralayer exchange couplings,the anisotropy,...The specific heats of both a two-layer ferromagnetic superlattice and a two-layer ferrimagnetic one arestudied.It is found that the spin quantum numbers,the interlayer and intralayer exchange couplings,the anisotropy,theapplied magnetic field,and the temperature all affect the specific heat of these superlattices.For both the ferromagneticand ferrimagnetic superlattices,the specific heat decreases with increasing the spin quantum number,the absolutevalue of interlayer exchange coupling,intralayer exchange coupling,and anisotropy,while it increases with increasingtemperature at low temperatures.When an applied magnetic field is enhanced,the specific heat decreases in the two-layerferromagnetic superlattice,while it is almost unchanged in the two-layer ferrimagnetic superlattice at low fieldrange at low temperatures.展开更多
The magnon energy band in a four-layer ferromagnetic superlattice is studied by using the linear spin-wave approach and Green's function technique. It is found that three modulated energy gaps exist in the magnon ...The magnon energy band in a four-layer ferromagnetic superlattice is studied by using the linear spin-wave approach and Green's function technique. It is found that three modulated energy gaps exist in the magnon energy band along Kx direction perpendicular to the superlattice plane. The spin quantum numbers and the interlayer exchange couplings all affect the three energy gaps. The magnon energy gaps of the four-layer ferromagnetic superlattice are different from those of the three-layer one. For the four-layer ferromagnetic superlattice, the disappearance of the magnon energy gaps Δω12, Δω23 and Δω34 all correlates with the symmetry of this system. The zero energy gap Δω23 correlates with the symmetry of interlayer exchange couplings, while the vanishing of the magnon energy gaps Δω12 and Δω34 corresponds to a translational symmetry of x-direction in the lattice. When the parameters of the system deviate from these symmetries, the three energy gaps will increase.展开更多
基金Supported by the Natural Science Foundation of Liaoning Province of China under Grant No. 20062040
文摘The frequency in middle of magnon energy band in a five-layer ferromagnetic superlattice is studied byusing the linear spin-wave approach and Green's function technique.It is found that four energy gaps and correspondingfour frequencie in middle of energy gaps exist in the magnon band along K_x direction perpendicular to the superlatticeplane.The spin quantum numbers and the interlayer exchange couplings all affect the four frequencies in middle of theenergy gaps.When all interlayer exchange couplings are same, the effect of spin quantum numbers on the frequency ω_(g1)in middle of the energy gap Δω_(12) is complicated, and the frequency ω_(g1) depends on the match of spin quantum numbersin each layer.Meanwhile, the frequencies ω_(g2), ω_(g3), and ω_(g4) in middle of other energy gaps increase monotonously withincreasing spin quantum numbers.When the spin quantum numbers in each layer are same, the frequencies ω_(g1), ω_(g2),ω_(g3), and ω_(g4) all increase monotonously with increasing interlayer exchange couplings.
基金Supported by the Natural Science Foundation of Liaoning Province of China under Grant No.20062040
文摘The specific heats of both a two-layer ferromagnetic superlattice and a two-layer ferrimagnetic one arestudied.It is found that the spin quantum numbers,the interlayer and intralayer exchange couplings,the anisotropy,theapplied magnetic field,and the temperature all affect the specific heat of these superlattices.For both the ferromagneticand ferrimagnetic superlattices,the specific heat decreases with increasing the spin quantum number,the absolutevalue of interlayer exchange coupling,intralayer exchange coupling,and anisotropy,while it increases with increasingtemperature at low temperatures.When an applied magnetic field is enhanced,the specific heat decreases in the two-layerferromagnetic superlattice,while it is almost unchanged in the two-layer ferrimagnetic superlattice at low fieldrange at low temperatures.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 50331030, 10674139 and 10274087)the Natural Science Foundation of Liaoning Province, China (Grant No 20062040)
文摘The magnon energy band in a four-layer ferromagnetic superlattice is studied by using the linear spin-wave approach and Green's function technique. It is found that three modulated energy gaps exist in the magnon energy band along Kx direction perpendicular to the superlattice plane. The spin quantum numbers and the interlayer exchange couplings all affect the three energy gaps. The magnon energy gaps of the four-layer ferromagnetic superlattice are different from those of the three-layer one. For the four-layer ferromagnetic superlattice, the disappearance of the magnon energy gaps Δω12, Δω23 and Δω34 all correlates with the symmetry of this system. The zero energy gap Δω23 correlates with the symmetry of interlayer exchange couplings, while the vanishing of the magnon energy gaps Δω12 and Δω34 corresponds to a translational symmetry of x-direction in the lattice. When the parameters of the system deviate from these symmetries, the three energy gaps will increase.
