The effect of Ba-site substitution on the magnetic behavior of ordered perovskite RBaMn2O6 (R = rare earth)

• RBa1−xAexMn2O6 (R = rare-earth, Ae = Ca, Sr) have been synthesized.
• The magnetic properties have been investigated.
• Ba-site substitution reduces TAAFTAAF and TCOTCO.
• Effect of structural randomness due to Ba-site substitution is dominant at R = Nd.

We have investigated the effect of Ba-site substitution with Ae (Ae = Sr and Ca) on the magnetic properties of A-site ordered RBaMn2O6 with R = Pr, Nd, and Nd0.5Sm0.5. Ba-site substitution reduces the mismatch between the average ionic radii of R- and Ba-sites, but introduces structural randomness into Ba-site. A reduction in the R/Ba mismatch suppresses the charge/orbital ordered insulating (COOI) state of Nd0.5Sm0.5BaMn2O6 and the A-type antiferromagnetic (AAF) one of PrBaMn2O6, while the Curie temperature of PrBaMn2O6 is almost insensitive to Ba-site substitution. At the multicritical point where the COOI, AAF, and ferromagnetic metallic (FM) states meet, the effect of the structural randomness is dominant; with increasing the structural randomness, the FM and AAF transition temperatures of NdBaMn2O6 decrease.

(a) Variation in TCOTCO of Nd0.5Sm0.5Ba1−xAexMn2O6Nd0.5Sm0.5Ba1−xAexMn2O6 and TAAFTAAF of PrBa1−xAexMn2O6PrBa1−xAexMn2O6 as a function of the average ionic radius of Ba1−xAexBa1−xAex (rBarBa). (b) Variation in TAAFTAAF and TCTC of NdBa1−xAexMn2O6NdBa1−xAexMn2O6 as a function of the structural randomness σ2σ2 of Ba1−xAexBa1−xAex-site.Figure optionsDownload as PowerPoint slide