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We report the properties of an A-site spinel magnet, CoAl2−xGaxO4, and analyze its anomalous, low-temperature magnetic behavior, which is derived from inherent, magnetically frustrated interactions. Rietveld analysis of the x-ray diffraction profile for CoAl2−xGaxO4 revealed that the metallic ions were randomly distributed in the tetrahedral (A-) and octahedral (B-) sites in the cubic spinel structure. The inversion parameter eta could be controlled by varying the gallium (Ga) composition in the range 0.055 ≤ eta ≤ 0.664. The composition-induced Néel-to-spin-glass (NSG) transition occurred between 0.05 ≤ eta ≤ 0.08 and was verified by measurements of DC-AC susceptibilities chi and thermoremanent magnetization (TRM) below the Néel transition temperature TN. The relaxation rate and derivative with respect to temperature of TRM increased at both TN and the spin glass (SG) transition temperature TSG. The TRM decayed rapidly above and below these transitions. TRM was highly sensitive to macroscopic magnetic transitions that occurred in both the Néel and SG phases of CoAl2−xGaxO4. In the vicinity of the NSG boundary, there was a maximum of the TRM relaxation rate at Tmax < TN. With increasing inversion eta(x), the anomaly at Tmax merged with that of the Néel transition at a tricritical point (etatc, Ttc) = (0.08, 4.0 K), where the paramagnetic, Néel, and SG states met. We successfully extracted the relaxation time tau and other characteristic parameters from the TRM isothermal temporal evolution based on the Weron function derived for a purely stochastic process. To distinguish the magnetic states, we compared our results with previously studied inversion-free A-site spinel, CoRh2O4, and CoGa2O4 cluster glass.

権利情報:

• In Copyright
  

  This is an author-created, un-copyedited version of an article accepted for publication/published in JOURNAL OF PHYSICS-CONDENSED MATTER. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at https://doi.org/10.1088/1361-648X/ad12fc.

キーワード: magnetic frustration, thermoremanent magnetization, magnetic phase diagram, quantum critical point

刊行年月日: 2024-03-27

出版者: IOP Publishing

掲載誌:

• JOURNAL OF PHYSICS-CONDENSED MATTER (ISSN: 1361648X) vol. 36 issue. 12 p. 125801-125801

研究助成金:

原稿種別: 査読前原稿 (Author's original)

MDR DOI: https://doi.org/10.48505/nims.4312

公開URL: https://doi.org/10.1088/1361-648X/ad12fc

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更新時刻: 2024-01-05 22:11:13 +0900

MDRでの公開時刻: 2023-12-25 16:30:27 +0900