Local positional and spin symmetry breaking as a source of magnetism and insulation in paramagnetic EuTi O3

Journal Article · Mon Mar 28 00:00:00 EDT 2022 · Physical Review Materials

DOI:https://doi.org/10.1103/physrevmaterials.6.034604· OSTI ID:1980343

Malyi, Oleksandr I. ^[1]; Zhao, Xin-Gang ^[2]; Bussmann-Holder, Annette ^[3]; Zunger, Alex ^[2]

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1. Univ. of Colorado, Boulder, CO (United States); OSTI
2. Univ. of Colorado, Boulder, CO (United States)
3. Max Planck Institute of Solid State Research, Stuttgart (Germany)

Here we consider theoretically the paramagnetic phases of EuTiO₃ that represent configurations created by two sets of microscopic degrees of freedom (m-DOFs): positional symmetry breaking due to octahedral rotations and magnetic symmetry breaking due to spin disorder. The effect of these sets of m-DOFs on the electronic structure and properties of the para phases is assessed by considering sufficiently large (super) cells with the required nominal global average symmetry, allowing, however, the $$\mathcal{local}$$ positional and magnetic symmetries to be lowered. We find that tendencies for local symmetry breaking can be monitored by following total energy lowering in mean-fieldlike density-functional theory, without recourse for strong correlation effects. While most nominally cubic ABO₃ perovskites are known for their symmetry breaking due to the B-atom sublattice, the case of f-electron magnetism in EuTiO₃ is associated with A-sublattice symmetry breaking and its coupling to structural distortions. We find that (i) paramagnetic $$\mathcal{cubic}$$ EuTiO₃ has an intrinsic tendency for both magnetic and positional symmetry breaking, while paramagnetic $$\mathcal{tetragonal}$$ EuTiO₃ has only magnetic symmetry lowering and no noticeable positional symmetry lowering with respect to low-temperature antiferromagnetic tetragonal phase. (ii) Properly modeled paramagnetic tetragonal and cubic EuTiO₃ have a nonzero local magnetic moment on each Eu ion, consistent with the experimental observations of local magnetism in the para phases of EuTiO₃ significantly above the Néel temperature. Interestingly, (iii) the local positional distortion modes in the short-range ordered para phases are inherited from the long-range ordered low-temperature antiferromagnetic ground-state phase.

• Research Organization: Univ. of Colorado, Boulder, CO (United States)
• Sponsoring Organization: National Science Foundation (NSF); USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division (MSE)
• Grant/Contract Number: SC0010467
• OSTI ID: 1980343
• Journal Information: Physical Review Materials, Journal Name: Physical Review Materials Journal Issue: 3 Vol. 6; ISSN 2475-9953
• Publisher: American Physical Society (APS)
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
Crystal structure
Electronic structure
First-principles calculations
Materials Science
Oxides
Paramagnetism
Phase transitions