Magnetic interactions in medium entropy oxide (4R) FeO3 single crystal (R-Sm, Er, Gd, Eu)

In this work, we successfully synthesized a medium-entropy oxide single crystal, (4R)FeO3, by incorporating four distinct rare-earth elements such as Sm, Er, Gd, and Eu at the A-site and a single transition metal, Fe3+, at the B-site. The crystal was grown using the optical floating zone method under an oxygen-rich atmosphere, yielding a high-quality single crystal approximately 5.2 cm in length. Powder x-ray diffraction confirmed the orthorhombic perovskite structure with space group Pbnm, verifying the phase purity of the material. Magnetic measurements revealed rich and complex magnetic behavior arising from the non-zero spin interactions between the R3+ and Fe3+ ions. Notably, a type-I spin switching transition (Sm3+–Fe3+–Er3+) was observed along the a axis at 22 K under a 50 Oe field in the zero-field-cooled magnetization curve. A pseudo-compensation temperature was also identified, characterized by a non-zero total magnetization of 0.05 emu/g, indicating antiparallel alignment between the rare-earth and iron sublattices. Furthermore, a spin reorientation transition in the range of 98–128 K (Γ4 → Γ2) was observed the highest transition temperature reported for perovskite systems incorporating four or more rare-earth ions at the A-site. The material also exhibited a large coercive field and small magnetization at 10 K, as well as electrical switching in the M–H loop at 20 K, indicating strong coupling to the magnetic flux density. These results highlight the potential of (4R)FeO3 as a promising candidate for spin-based device applications.