Title

Mössbauer Spectroscopy Of Ferromagnetic Oxygen-Rich Dicalcium Cuprate Ca2Cuo3+Δ

Abstract

Stoichiometric Ca2CuO3 qualifies as a low-dimensional antiferromagnet. Nonetheless, oxygenated sintered samples of high-purity Ca2CuO3+δ, δ ≅ 0.17, exhibited remarkable spontaneous ferromagnetic hysteresis at ambient conditions [1-3]. In this work, Mössbauer fitting of spectroscopic data on Ca2Cu0.98557Fe0.015 O3+δ revealed large magnetic hyperfine fields at two sites, indicative of FeIII charge state, combined with fairly large electric quadrupole interaction parameters, as well as two central quadrupole-split doublets. One sextet, having B = 49 T, corresponds to the tetragonal copper ferrite spinel. The other sextet, with unusual B = 42 T and greater relative intensity variability following annealing in vacuum and post-oxygenation treatments, allows us to assign it to 57Fe substitution in dicalcium cuprate grain surfaces. This also supports the tentative interpretation in [1] for the ferromagnetism in pristine phase as excess holes-driven double exchange. One of the central doublets, with ΔEQ = 0.3 mm/s, is assigned to in-grain substitution in dicalcium cuprate, while a small-intensity doublet, having ΔEQ = 2.2 mm/s and CS = 0.6 mm/s, is assigned to 57FeIIxCu1-xO.

Publication Date

12-1-1999

Publication Title

Hyperfine Interactions

Volume

120-121

Issue

1-8

Number of Pages

507-512

Document Type

Article

Personal Identifier

scopus

Socpus ID

17444439176 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/17444439176

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