Semiconducting spin glass to metallic ferromagnetic state phase transition in double-substituted La1−xSrxCo1−y

Probing the incoherent admixture of low and high-spin states of Co in (LaPr)CoO3 perovskite: focus on structural phase transitions

“…LaCoO 3 is a well-studied compound since its inception around the 1950s which is a subject of broad and continuing interest to this day because this system exhibits a robust orbital order and a very stable ferromagnetic (FM) ordering below 85 K. This orbital ordering is associated with the intermediate-spin configuration (admixture of low-spin (LS) and high-spin (HS) states) of trivalent Co noticed in LaCoO 3 system both in the form of bulk polycrystals and thin filmnanostructures [9,10]. Also, anomalous changes in the temperature dependence of resistivity and magnetic susceptibility below 100 K have drawn special attention on this system as the electronic state of the trivalent cobalt ion fluctuates from LS state (S = 0; t 6 2g e 0 g ) to the HS (S = 2; t 4 2g e 2 g ) because of the sturdy competition between the crystal-field splitting (∆ cf ) and the Hund's intra-atomic exchange interactions (J ex ) with increasing temperature [9,[11][12][13][14]. This spin-state evolution reflects a redistribution of electrons between the t 2g and e g levels in LaCoO 3 with an approximate magnitude of ∆ cf equal to 1.93 eV estimated through the local density approximation (LDA) calculations which is slightly larger than ∆ cf ∼ 1.5 eV for Mn based fluorides which shows a similar admixture of electronic states [12,15].…”