DPG Phi
Verhandlungen
Verhandlungen
DPG

Dresden 2009 – scientific programme

Parts | Days | Selection | Search | Downloads | Help

MA: Fachverband Magnetismus

MA 3: Magnetic Half Metals and Oxides

MA 3.4: Talk

Monday, March 23, 2009, 11:45–12:00, HSZ 401

Correlation effects in p-electron magnets: the case of RbO2 — •Roman Kováčik and Claude Ederer — School of Physics, Trinity College Dublin, Dublin 2, Ireland

The development of spintronics in recent years has triggered a need for new materials such as half metallic (HM) ferromagnets. HM materials with 2p-magnetism were proposed from electronic structure calculations, e.g. Rb4O6 [1]. However, recent measurements indicate that Rb4O6 is a magnetically frustrated system that exhibits spin-glass-like behavior in a magnetic field [2]. This discrepancy was attributed to inadequate treatment of the molecular states within the local spin density approximation (LSDA). This assumption was supported by calculations for RbO2, known to be an insulating antiferromagnet, which turns out to be HM in LSDA as well. According to [2], this outcome could not be corrected within LDA+U even for U=13.6 eV.

We present results of LDA+U calculations for RbO2, which show that, when allowing the system to reduce its symmetry, an orbitally polarized insulating state is favored for U>2 eV, consistent with experiment. Furthermore, we discuss an alternative treatment of on-site correlations in RbO2, using an effective tight-binding model corresponding to a molecular orbital basis, which is constructed via maximally localized Wannier functions. In this case, the insulating state is obtained for significantly lower U>0.5 eV. In addition, we discuss a possible orbital ordering driven by correlation effects.

[1] J. J. Attema et al., J. Am. Chem. Soc. 127, 16325 (2005).

[2] J. Winterlik et al., J. Phys. Condens. Matter 19, 1 (2007).

100% | Mobile Layout | Deutsche Version | Contact/Imprint/Privacy
DPG-Physik > DPG-Verhandlungen > 2009 > Dresden