Commun. Comput. Phys., 13 (2013), pp. 526-539.


Investigation of Possible Half-Metallic Antiferromagnets on Double Perovskites A_2 BB'O_6 (A=Ca, Sr Ba; B,B'=Transition Metal Elements)

S. H. Chen 1*, Z. R. Xiao 2, Y. P. Liu 3, Y. K. Wang 4*

1 Institute of Physics, Academia Sinica, Taipei 11529, Taiwan.
2 Graduate Institute of Applied Physics, National Chengchi University, Taipei 11605, Taiwan.
3 Department of Physics, National Taiwan Normal University, Taipei 106, Taiwan.
4 Center for General Education and Department of Physics, National Taiwan Normal University, Taipei 106, Taiwan.

Received 30 September 2011; Accepted (in revised version) 9 March 2012
Available online 17 July 2012
doi:10.4208/cicp.300911.090312a

Abstract

A search was made for possible half-metallic (HM) antiferromagnet (AFM) in all the (C^29_2=406) double perovskites structures of Sr_2 BB'O_6 where BB' pairs are any combination of 3d, 4d or 5d transition elements with the exception of La. Sr can also be replaced by Ca or Ba whenever HM-AFM was found and similar calculations were then performed in order to probe further possibilities. It was found that A_2 MoOsO_6, A_2 TcReO_6, A_2 CrRuO_6, where A=Ca, Sr, Ba, are all potential candidates for HM-AFM. The AFM of A_2BB'O_6 comes from both the superexchange mechanism and the generalized double exchange mechanism via the B(t_{2g})-O2p_{\pi}-B'(t_{2g}) coupling, With the latter also being the origin of their HM. Also considered were the effects of spin-orbit coupling (SOC) and correlation (+U) by introducing +SOC and +U corrections. It is found that the SOC effect has much less influence than the correlation effect on the HM property of the compounds. For A_2 TcReO_6 and A_2 CrRuO_6, after +U, they become nearly Mott-Insulators. In the future, it is hoped that there will be further experimental confirmation for these possible HM-AFM candidates.


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PACS: 75.10.Lp, 71.20.-b, 75.30.-m, 75.50.Ee
Key words: Half-metal antiferromagnet, GGA +U, superexchange, generalized double exchange.

*Corresponding author.
Email: chen_shao_hua197@yahoo.com.tw (S. H. Chen), zrxiao@gmail.com (Z. R. Xiao), viva.guitarra@gmail.com (Y. P. Liu), kant@ntnu.edu.tw (Y. K. Wang)
 

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