Investigations Of Spin Hamiltonian Parameters And Local Structure For K₂CrO₄:Mn⁶⁺ Crystal

3d¹ ions(Ti³⁺,V⁴⁺,Cr⁵⁺and Mn⁶⁺)are common doped ions in optical material crystals.With the wide application of artificial crystal in military,architectural,medical and scientific research,crystals doped with 3d¹ions have attracted much attention.The optical and magnetic properties of the complex crystals depend to a large extent on the local structure near the complex ions.The absorption spectra and electron paramagnetic resonance spectra（EPR spectra）of the crystals are also closely related to the local structure of the complex ions in the crystals.Therefore,the studies of the spin Hamiltonian parameters（EPR parameters）and absorption spectra of these crystals is an important means to study the local structure of complex ions.It is also an important method for people to understand and master the properties of crystals.However,the analysis and studies of the EPR parameters are not deep enough,which mainly reflects the following shortcomings:Because the origin of electron paramagnetic resonance spectrum of crystals is very complex.This is a common result of the crystal field（CF）mechanism,the charge-transfer（CT）mechanism,the Jahn-Teller effect and another mechanism.The contribution of CF mechanism to EPR parameters（g factor and A value）is relatively large.Therefore,the calculation of EPR parameters has neglected other mechanisms and only considered CF mechanism.However,this approximate calculation method is rough,and the theoretical explanation of the experimental results is not perfect.The doped ions studied are Mn⁶⁺in this paper,the valence state of this ion is high and it has strong covalence with host crystal.Therefore,the effect of charge transfer on the results should be considered when studying the EPR phenomenon of its complex.The main work of this paper is as follows:The local structure and absorption spectrum of tetrahedron in the crystal are analyzed by overlap model and crystal field theory,and the crystal field parameters and the distortion information of tetrahedron are obtained.Based on the double mechanism（CF mechanism and CT mechanism）and the Jahn-Teller effect,the high-order perturbation formula for calculating the spin Hamiltonian parameters of3d¹ions in tetrahedron is derived under the double-spin-orbit coupling parameter model,and the EPR parameters of the crystal are calculated.The effect of CT mechanism and CF mechanism on the results was compared and analyzed.Among them,the ratio of the contribution of the CT mechanism and the CF mechanism to the EPR parameters is about 30%to 60%（corresponding to the different direction）.The contribution of CT mechanism is larger than the third-order perturbation of CF mechanism to the g factor.The influence factor of Jahn-Teller effect on A value is N（7）e（8）?0.69,which is larger than the default value of 1.The results show that the CT mechanism cannot be ignored when calculating the EPR parameters of the crystal,and the Jahn-Teller effect should also be considered when calculating the A value of this crystal.