Abstract
is a double perovskite (DP) with symmetry based on the ion, , , . It is isostructural with , the magnetic ground state of which is apparently a very unusual collective spin singlet or valence-bond glass state as is the case for cubic () . Initial studies of suggested a different ground state from the other DPs but no clear conclusions could be drawn. A more detailed study is presented here including magnetic susceptibility, heat capacity, and elastic neutron-scattering results. This DP is now well characterized as an antiferromagnet, , via observation of magnetic Bragg peaks in neutron scattering and an anomaly in the magnetic heat capacity. The ordering wave vector is , consistent with a type I face-centered-cubic magnetic structure, and the ordered moment on is , much reduced from the spin-only value of . The index, , indicates a low level of frustration. The heat-capacity data above can be interpreted in terms of a one-dimensional spin-correlation model, as can the low-temperature data which follow a power law. This is consistent with an earlier suggestion. The difference with isostructural is attributed to differences in the local distortion of the Mo–O octahedron and the resulting orbital ordering.
- Received 30 April 2020
- Revised 7 August 2020
- Accepted 14 August 2020
DOI:https://doi.org/10.1103/PhysRevMaterials.4.104406
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