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Title: Successive spin reorientations and rare earth ordering in Nd0.5Dy0.5Fe O3: Experimental and ab initio investigations
Authors: Singh A.
Rajput S.
Balasubramanian P.
Anas M.
Damay F.
Kumar C.M.N.
Eguchi G.
Jain A.
Yusuf S.M.
Maitra, Tulika
Malik, Vivek K.
Published in: Physical Review B
Abstract: In the present paper, the magnetic structure and spin reorientation of mixed rare-earth orthoferrite Nd0.5Dy0.5FeO3 have been investigated. At room temperature, our neutron-diffraction measurements reveal that the magnetic structure of Fe3+ spins in Nd0.5Dy0.5FeO3 belongs to Γ4 irreducible representation (Gx, Fz) as observed in both parent compounds (NdFeO3 and DyFeO3). The neutron-diffraction study also confirms the presence of a spin-reorientation transition where the magnetic structure of Fe3+ spins changes from Γ4 to Γ2(Fx, Gz) representation between 75 and 20 K while maintaining a G-type antiferromagnetic configuration. Such a gradual spin reorientation is unusual since the large single ion anisotropy of Dy3+ ions is expected to cause an abrupt Γ4→1(Gy) rotation of the Fe3+ spins. At 10 K, the Fe3+ magnetic structure is represented by Γ2 (Fx, Gz). Unexpectedly, the Γ4 structure of Fe3+ spins re-emerges below 10 K, which also coincides with the development of rare-earth (Nd3+/Dy3+) magnetic ordering having cyR configuration. Such re-emergence of a magnetic structure has been a rare phenomenon in orthoferrites. The absence of a second-order phase transition in rare-earth ordering, interpreted from heat capacity data, suggests the prominent role of Nd3+-Fe3+ and Nd3+-Dy3+ exchange interactions. These interactions suppress the independent rare-earth magnetic ordering observed in both parent compounds due to Nd3+/Dy3+-Nd3+/Dy3+ exchange interactions. Our density-functional-theory calculations including Coulomb correlation and spin-orbit interaction effects (DFT+U+SO) reveal that the C-type arrangement of rare-earth ions (Nd3+/Dy3+), with Γ2 (Fx, Gz) configuration for Fe3+ moments, is energetically very close to a phase with the same rare-earth magnetic ordering but Γ4 (Gx, Fz) configuration of Fe3+ spins. Further, the Nd3+-Fe3+ and Nd3+-Dy3+ exchange interactions are observed to play significant roles in the complex Fe3+ spin reorientation with the re-emergence of Γ4 at low temperature. Consistent with the experimental observations, our calculations established the mixed phase (Γ2 and Γ4) to be the magnetic ground state of Fe3+ moments.
Citation: Physical Review B(2020), 102(14)
Issue Date: 2020
Publisher: American Physical Society
Keywords: Antiferromagnetism
Density functional theory
Exchange interactions
Ground state
Magnetic structure
Metal ions
Neutron diffraction
Rare earths
Specific heat
Spin orbit coupling
Ternary alloys
Ab initio investig
ISSN: 24699950
Author Scopus IDs: 57212846130
Author Affiliations: Singh, A., Department of Physics, Indian Institute of Technology Roorkee, Roorkee, 247 667, India
Rajput, S., Department of Physics, Indian Institute of Technology Roorkee, Roorkee, 247 667, India
Balasubramanian, P., Graphic Era University, Dehradun, 2
Funding Details: .Center for Strategic Research, CSR Science and Engineering Research Board, SERB: CRS-M-228, ECR/2015/000136 Indian Institute of Technology Roorkee, IITR.This work was supported by the UGC-DAE Consortium for Scientific Research (CSR) and Science and Engineering Research Board (SERB) through CRS-M-228, ECR/2015/000136, respectively. We acknowledge the support from IIT Roorkee through SMILE-13 grant. A.S. an
Corresponding Author: Malik, V.K.; Department of Physics, India; email:
Appears in Collections:Journal Publications [PH]

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