Coexisting magnetic structures and spin reorientation in Er0.5Dy0.5Fe0.3: Bulk magnetization, neutron scattering, specific heat, and density functional theory studies

The complex magnetic structures, spin reorientation, and associated exchange interactions have been investigated in Er0.5Dy0.5Fe0.3 using bulk magnetization, neutron diffraction, specific heat measurements, and density functional theory calculations. The Fe3+ spins order as G-type antiferromagnet structure depicted by Gamma(4)(G(x), A(y), F-z) irreducible representation below 700 K, similar to its end compounds. The bulk magnetization data indicate occurrence of the spin-reorientation and rare-earth magnetic moments' polarization below similar to 75 K and 10 K, respectively. The neutron diffraction studies confirm an "incomplete" Gamma(4)-> Gamma(2)(F-x, C-y, G(z)) spin-reorientation initiated <= 75 K. Although the relative volume fraction of the two magnetic structures varies with decreasing temperature, both coexist even at 1.5 K. Below 10 K, the polarization of Er3+/Dy3+ moments in c(y)(R) arrangement develops, which gradually increases with decreasing temperature. At 2 K, magnetic structure associated with c(z)(R) arrangement of Er3+/Dy3+ moments also appears. At 1.5 K, while the rare-earth magnetic moments show c(y)(R) + c(z)(R)-type arrangement, the Fe3+ spins are represented by a combination of a Gamma(2)+Gamma(4)(G(z), G(x)) arrangement. A clear signature of the magnetic structure with Gamma(1)(G(y)) representation, symmetrically compatible with the c(z)(R)-type arrangement of rare-earth moments, is not confirmed from the refinement of the neutron diffraction data. The observed Schottky anomaly at 2.5 K suggests that the "rare-earth ordering" is induced by polarization due to Fe3+ spins. The Er3+-Fe3+ and Er3+-Dy3+ exchange interactions, obtained from first principle calculations, indicate that these interactions primarily cause the complicated spin reorientation and c R rare-earth ordering in the system, respectively, while the dipolar interactions between rare-earth moments result in the cf type rare-earth ordering at 2 K.