Coexisting magnetic structures and spin reorientation in Er 0.5 Dy 0.5 FeO 3 : Bulk magnetization, neutron scattering, specific heat, and density functional theory studies

International audienceThe complex magnetic structures, spin-reorientation and associated exchange interactions have been investigated in Er0.5Dy0.5FeO3 using bulk magnetization, neutron diffraction, specific heat measurements and density functional theory calculations. The Fe 3+ spins order as G-type antiferromagnet structure depicted by Γ4(Gx, Ay, Fz) irreducible representation below 700 K, similar to its end compounds. The bulk magnetization data indicate occurrence of the spin-reorientation and rare-earth magnetic ordering below ∼75 K and 10 K, respectively. The neutron diffraction studies confirm an "incomplete" Γ4→ Γ2(Fx, Cy, Gz) spin-reorientation initiated ≤75 K. Although, the relative volume fraction of the two magnetic structures varies with decreasing temperature, both co-exist even at 1.5 K. Below 10 K, magnetic ordering of Er 3+ /Dy 3+ moments in c R y arrangement develops, which gradually increases in intensity with decreasing temperature. At 2 K, magnetic structure associated with c R z arrangement of Er 3+ /Dy 3+ moments also appears. At 1.5 K the magnetic structure of Fe 3+ spins is represented by a combination of Γ2+Γ4+Γ1, while the rare earth magnetic moments' order coexists as c R y and c R z corresponding to Γ2 and Γ1 representation, respectively. The observed Schottky anomaly at 2.5 K suggests that the "rare-earth ordering" is induced by polarization due to Fe 3+ spins. The Er 3+-Fe 3+ and Er 3+-Dy 3+ exchange interactions, obtained from first principle calculations, indicate that these interactions primarily cause the complicated spin-reorientation and c R y rare-earth ordering in the system, respectively, while the dipolar interactions between rare-earth moments, result in the c R z type rare-earth ordering at 2 K