期刊
JOURNAL OF PHYSICAL CHEMISTRY C
卷 117, 期 35, 页码 18190-18198出版社
AMER CHEMICAL SOC
DOI: 10.1021/jp405382t
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资金
- ANR [ANR-09-BLAN-0187-01]
- Fonds Europeen de Developpement Regional (FEDER)
- CNRS
- Region Nord Pas-de-Calais
- Ministere de l'Enseignement Superieur et de la Recherche
- ENS of Lyon
- Agence Nationale de la Recherche (ANR) [ANR-09-BLAN-0187] Funding Source: Agence Nationale de la Recherche (ANR)
BaCo2X2O7 (X = P, As) compounds are formed of chains of Co2+O8 dimers. In a first approximation, the structural chains appear strongly isolated, which gives a pronounced one-dimensiona (1D) magnetic character to the systems. GGA+U calculations show ferromagnetic (FM) exchanges inside the dimers and predominant antiferromagnetic coupling between them along the chains, as confirmed by the refined magnetic structure. This ID antiferromagnetic topology between S = 3 FM dimers does not support the existence of two broad overlapped magnetization plateaus observed around H-c1 = 5 T (ferrimagnetic state -> similar to Ms/3) and H-c2 = 7 T (ferromagnetic state -> Ms). In the crystal, an incommensurate structural modulation promotes important atomic displacement waves that transform the ID chains into two-dimensional layers. In the layers, strongly frustrated topologies between Co2+ triangles of S = 3 dimers are distributed accordingly to the modulation wave. The exchanges calculated for the maximal frustrated geometry offered by the modulation show that they are mainly responsible for the stepped magnetization.
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