Strain induced phase transition in La$$_0.2$$Sr$$_0.8$$MnO$$₃$$

We explore the structural and magnetic tunability of polycrystalline La(_0.2)Sr(_0.8)MnO(_3) sample by varying preparation conditions using solid state reaction method. Low temperature X-ray diffraction studies indicate that one of the samples shows a transition from cubic Pm-3m structure to dominant tetragonal I4/mcm structure below (sim)260K, while the other sample exhibits transformation from cubic structure to a dominant phase with fundamental reflections corresponding to P4/mmm tetragonal symmetry below (sim)260K, followed by an incomplete transition from this phase to tetragonal I4/mcm phase below (sim)225K. The Rietveld analysis at 260K indicates that the former sample exhibits co-existence of cubic Pm-3m, tetragonal I4/mcm and P4/mmm phases while the latter sample shows the co-existence of Pm-3m and tetragonal P4/mmm phases. Density functional theory(DFT+U) calculations suggest C-type antiferromagnetic and ({d}_3z^2-r^2) orbital ordering in I4/mcm structure and A-type antiferromagnetic with ({d}_x^2-y^2) orbital ordering in P4/mmm structure. The results show a possibility of tuning magnetic structure from C-type antiferromagnetic to A-type antiferromagnetic in an intermediate temperature range at fixed concentration, by varying the strain fields. At high temperatures(300–518K), the resistivity follows small polaron hopping model in both the samples and change in preparation conditions leads to a change over from adibatic to non-adibatic limit.Above 518K, both the samples exhibit metallic resistivity. Our results open a new avenue for tuning magnetic and structural phases in phase separated systems, and such tunability may be useful in antiferromagnetic spintronic, designing correlated electron-based electronic devices.