Microscopic evidence of spin state order and spin state phase separation in layered cobaltites RBaCo2O5.5 with R=Y, Tb, Dy, and Ho.

Microscopic evidence of spin state order and spin state phase separation in layered cobaltites RBaCo2O5.5 with R=Y, Tb, Dy, and Ho.

Physical review letters (2008-09-04)

H Luetkens, M Stingaciu, Yu G Pashkevich, K Conder, E Pomjakushina, A A Gusev, K V Lamonova, P Lemmens, H-H Klauss

摘要

We report muon-spin relaxation measurements on the magnetic structures of RBaCo2O(5.5) with R=Y, Tb, Dy, and Ho. Three different phases, one ferrimagnetic and two antiferromagnetic, are identified below 300 K. They consist of different ordered spin state arrangements of high-, intermediate-, and low-spin Co3+ of CoO6 octahedra. Phase separation into well separated regions with different spin state order is observed in the antiferromagnetic phases. The unusual strongly anisotropic magnetoresistance and its onset at the FM-AFM phase boundary is explained.