A-site heterovalency induced cationic disorder effects on the structural, electronic, and magnetic properties of double perovskite: Sr2FeMnO6

The 5 s/6 s (A-site)-3d (B-site) based double perovskites enounce multiple aspects to study the interactive effects on structural (global and local), electronic, and other physical properties of synthesized compounds. The characteristic feature of this family is the B-site cations, which have comparative ionic radii and multivalency. Here, we report a detailed analysis of the structural, electronic, and magnetic properties of Sr$_2$FeMnO$_6$ (SFMO) and La-substituted SrLaFeMnO$_6$ (SLFMO). The relatively smaller radii but large valance La$³⁺$ (1.36 Å) substitution at Sr$²⁺$ (1.44 Å) sites led to adequate changes in the structural and physical properties. SLFMO crystallized in a lower crystal symmetry than SFMO, further confirmed by Raman analysis. Spectroscopic analyses showed that the Mn-valency compensates for the cationic disorder introduced by the La-substitution. These analyses also revealed that Mn and Fe preserve high spin states of their 3+ and 4+ valence states, and thus, the studied compounds also have Jahn-Teller (JT) distortion. These structural and electronic distortions affect the magnetic properties of SFMO and SLFMO. SFMO showed antiferromagnetic behavior, while SLFMO showed spin-glass-type characteristics.