The Mn-terminated (001) surface of the stable antiferromagnetic insulating phase of the cubic perovskite CaMnO3 was found to undergo a magnetic reconstruction consisting of a spin-flip process at the surface: Each Mn spin at the surface flips to pair with one in the sub-surface layer. In spite of very little Mn-O charge transfer at the surface, the behaviour was driven by the eg states due to the dxy → dz2 charge redistribution. These results, based on local spin density theory, give a double-exchange-like coupling that was driven by the eg character, not the additional charge, and could have relevance to colossal magnetoresistive materials.

Magnetic Reconstruction at the (001) CaMnO3 Surface. A.Filippetti, W.E.Pickett: Physical Review Letters, 1999, 83, 4184-7