Energy-loss magnetic circular dichroism measurements of ferromagnetic ordering in LaSrCoO$_3$

Experimental results show that tuning the ferromagnetism of LaSrCoO$_3$ can be achieved at various temperatures by doping bulk sample with smaller atoms or straining thin film sample. In this work, we will use 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 in-situ heating and cooling experiments to examine the magnetic and spin-state transitions in La$_{\mathrm{1-x}}$Sr$_{\mathrm{x}}$CoO$_3$ (x$=$0-0.3) between 80 K and 600 K. Using energy-loss magnetic circular dichroism method, we confirm the magnetic ordering transition at room temperature with increasing doping concentrations. Differences in the O K- and Co-L-edges will be utilized to determine the Co valence of the samples. A magnetic transition is observed in 5{\%} doped sample during in-situ cooling experiment to 95 K. Additionally, with increasing the doping concentration, a change in crystal structure is measured using ABF imaging, more specifically a distortion of the CoO$_6$ octahedra.