Magnetization Steps Promoted by Structural Modulation in BaCoX2O7 (X = As, P)

详细信息    查看全文

• 作者：R茅nald David ; Houria Kabbour ; Silviu Colis ; Alain Pautrat ; Emmanuelle Suard ; Olivier Mentr茅
• 刊名：Journal of Physical Chemistry C
• 出版年：2013
• 出版时间：September 5, 2013
• 年：2013
• 卷：117
• 期：35
• 页码：18190-18198
• 全文大小：579K
• 年卷期：v.117,no.35(September 5, 2013)
• ISSN：1932-7455

文摘

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 1D 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 鈫?Ms/3) and H_c2 = 7 T (ferromagnetic state 鈫?Ms). In the crystal, an incommensurate structural modulation promotes important atomic displacement waves that transform the 1D 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.