Magnetization Distribution in the layered CMR Manganite La1.2Sr1.8Mn2O7 from Polarized Neutron Diffraction

Abstract

In the ferromagnetic metallic state of the colossal magnetoresistive (CMR) manganite La1.2Sr1.8Mn2O7, the spin density distribution is essentially in agreement with the standard picture in which the unpaired electrons occupy the three t2g orbitals, dxy, dyz, and dxz. However we find a small spin density ~4% of the total Mn spin) on the apical O(2) oxygen atom at both 100 K and 220 K and we suggest that this is due to covalency effects. Surprisingly we find no evidence of spin on the other apical oxygen O(1) suggesting that the Mn eg electron distribution along the c-axis is highly anisotropic.

5 pages, 2 figures. Physical Review B (in press)