Local Spin State Measurements in Critically Doped $La_{0.83} Sr_{0.17} CO_{3} $*

Strontium doped $LaCO_{3} $ has fascinating magnetic phases which are believed to be directly related to Co spin states. Critically doped $La_{0.83} Sr_{0.17} CO_{3} $ undergoes a simultaneous Insulator to Metal Transition (IMT) and ferromagnetic (FM) order transition. In this work, we will utilized atomic-resolution Z-contrast imaging, annular bright field (ABF) imaging and electron energy-loss spectroscopy in the aberration-corrected JEOL JEM-ARM200CF in combination with cooling experiments to examine the local magnetic and spin-state transitions in critically doped $La_{0.83} Sr_{0.17} CO_{3} $ between 80 K and 300 K. Our energy-loss magnetic circular dichroism (EMCD) experiments confirm the non-localized increase in the dichromatic signal at low temperature, associated with a change in the co-ion spin state. On the other hand, by using he ABF imaging, a distortion of the $CO_{6} $ octahedral and the changes in the Co-O bond lengths within the same unit cell are observed.