Spin Wave And Magnetic Quantum Behavior Of A Three-Layer Magnetic System With Body-centered Cubic Configuration

Due to multilayer magnetic thin films have broad application prospects in the fields of magnetic recording materials,magnetic resonance absorbing materials and spintronic devices,many theoretical and experimental researchers have been attracted to study their properties in recent years.A three-layer magnetic system with four sublattice body-centered cubic configurations is established in the framework of Heisenberg model.The linear spin wave theory and the delayed Green function method are used to diagonalize the Hamiltonian of the system.The spin spectra of the system without considering the next-nearest neighbor interaction and considering the next-nearest neighbor interaction are calculated respectively.Based on the spectral theorem and correlation function,the expressions of magnetic moment and quantum fluctuation in the ground state of the system are derived.Finally,the influence of exchange coupling,magnetic crystal anisotropy and spin quantum number on the energy gap,resonance frequency,ground state magnetic moment and quantum fluctuation in the ground state are studied and discussed by using the method of control variables.Finally,by horizontal comparison of the contents of the two cases,it is concluded that it is necessary to consider the influence of the next nearest neighbor interaction of the system.There are four spin spectra in the system and three energy gaps in the system can be seen from the energy spectra without considering the next-nearest neighbor interaction（only the nearest neighbor interaction）.Compared with magnetocrystalline anisotropy,spin quantum number and exchange coupling have more obvious effects on the energy gap of the system.The spin quantum numbers of A,B and D sublattices with spin direction up have obvious influence on the resonance frequencyf₄,while the spin quantum numbers of C sublattices with spin direction down have the greatest influence on the resonance frequencyf₁.The four resonant frequencies increase linearly with the increase of interlayer anisotropy,and the resonant frequencyf₁ changes the most.The effect of antiferromagnetic exchange coupling on resonance frequencyf₁ is the most obvious,and the effect of ferromagnetic exchange coupling on resonance frequencyf₄ is the most obvious.Compared with the ferromagnetic exchange coupling,the antiferromagnetic exchange coupling has more effect on the magnetic moment and quantum fluctuation in the ground state of the system.For the magnetocrystalline anisotropy,it has the most obvious influence on the magnetic momentM₃ and quantum fluctuation（35）M₃ in the ground state of the system.If the second nearest neighbor interaction is considered,there is only one energy gap in the system.It is found that the antiferromagnetic exchange coupling between the B and C sublattice has the greatest influence on the system’s energy gap,and the ferromagnetic exchange coupling between the A and B sublattice within the layer has the most obvious influence on the system’s energy gap.Both spin quantum number and magnetic crystal anisotropy have great influence on the system energy gap.In terms of resonance frequency,the four spin quantum numbers have obvious influences on resonance frequencyf₁,f₃andf₄.Interlayer anisotropyD_Z can significantly improve the resonant frequency of the system.The effect of antiferromagnetic exchange coupling on resonance frequencyf₁ is the most obvious,and the effect of ferromagnetic exchange coupling on resonance frequencyf₃ andf₄ is greater.The four kinds of magnetic crystal anisotropy have the most obvious influence on the magnetic momentM₃ and quantum fluctuation（35）M₃ in the ground state.Compared with ferromagnetic exchange coupling,the effect of antiferromagnetic exchange coupling on the magnetic moment and quantum fluctuation in the ground state is more obvious.In this thesis,by studying the correlation properties of the two systems,the influence of spin quantum number on the resonance frequency of the system,the influence of interlayer anisotropy and the exchange coupling between the nearest neighbor sublattices on the spin wave and magnetic quantum behavior of the system are compared laterally.Finally,it is concluded that the influence of the second nearest neighbor interaction of the system cannot be ignored.