[Wien] A plausible magnetic moment from FSM calculation

[王静]

Hi, there
  Recently, I am doing some FSM calculations in transition metal oxides to find the relationship between spin magnetic moment and energy. Surprisingly, I have got the lowest energy with an unreasonable magnetic moment. The electronic configurations are d8 and d7 for the two transition metals and the total valence should be 8+. I set the spin moment value from 0.0μB to 5.0μB with the step of 0.5. Within GGA calculation, the lowest energy is found at 1.0μB which mean a (d6, d1)8+ state and the d6 in low spin. Nevertheless, in GGA+U calculation, the lowest state is found with a net spin moment of 4.0μB, including 3.99μB and -0.34μB on the transition metals and the others on the interstitial region and oxygen. The DOS pattern is most likely to be consistent with the (d6, HS; d1)8+ configuration, but this configuration will give rise to a net spin moment of 3μB. 
  Considering the fact that ferromagnetically coupled manner for d6(HS) and d1 would lead to a net moment of 5.0μB. One plausible explanation is that the two magnetic coupled manners are energetically degenerated. But this could not explain the opposite sign for the two transition metals. Other ferromagnetic scenery also do not fit the magnetic moment. So I beg some suggestions, or do I misunderstand something with the FSM method?


	

                 Jing Wang
　　　　　　　　wangjingjing at ciac.jl.cn
　　　　　　　　　　2013-05-11