Critical behavior of the half-doped perovskite Pr0.5Sr0.5CoO3−Δ
Critical behavior of the half-doped perovskite Pr0.5Sr0.5CoO3−Δ
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DOI：
10.1016/j.jallcom.2013.10.216
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发表时间：
2014-03
影响因子：
6.2
通讯作者：
Lei Zhang;Junfeng Fang;Jiyu Fan;M. Ge;L. Ling;Changjin Zhang;L. Pi;S. Tan;Yuheng Zhang
中科院分区：
文献类型：
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作者：
Lei Zhang;Junfeng Fang;Jiyu Fan;M. Ge;L. Ling;Changjin Zhang;L. Pi;S. Tan;Yuheng Zhang
采用体磁化强度法研究了半掺杂钙钛矿型钴酸盐Pr 0.5Sr0.5CoO3-Δ（Δ= 0，δ = 0.16）在临界温度附近的临界行为，得到了临界指数β，γ和δ.这些临界指数满足Widom标度律δ= 1+ γ β-1，表明所得结果具有自洽性和可靠性。随着临界指数的增加，M-T-H曲线在临界温度以下和临界温度以上坍缩成两个独立的普适分支。氧-非化学计量比Pr0.5Sr0.5CoO3-Δ体系的临界指数雅阁符合平均场模型。而对于氧化学计量的Pr 0.5Sr0.5CoO3，β偏离了三维Heisenberg模型的理论预测，而γ和δ则接近于平均场模型的理论预测.这些结果表明Pr 0.5 Sr 0.5 CoO 3− Δ（Δ= 0且Δ = 0.16）中存在长程铁磁耦合，这不能用双交换机制中提出的最近邻相互作用来解释。相反，p-d杂化和Pr 3+ f-电子与传导电子的RKKY相互作用的集体效应被认为是负责长程相互作用。此外，氧化学计量比Pr 0.5Sr0.5CoO3中β的差异可能是由于氧化学计量比样品中的晶外相所对应的短程相互作用所致。
Critical behaviors of the half-doped perovskite cobaltites Pr 0.5 Sr 0.5 CoO 3-Δ (Δ= 0 and∼ 0.16) are investigated around the critical temperatures by bulk magnetization study, where the critical exponents (β, γ and δ) are obtained. These critical exponents fulfill the Widom scaling law δ= 1+ γ β-1, indicating self-consistency and reliability of the obtained results. With the critical exponents, M–T–H curves collapse onto two independent universal branches below and above the critical temperatures. The critical exponents of the oxygen-nonstoichiometric Pr 0.5 Sr 0.5 CoO 3-Δ accord with the mean-field model exactly. However, for the oxygen-stoichiometric Pr 0.5 Sr 0.5 CoO 3, β deviates to the theoretical prediction of three-dimensional Heisenberg model while γ and δ are close to that of mean-field model. These results indicate long-range ferromagnetic coupling in Pr 0.5 Sr 0.5 CoO 3− Δ (Δ= 0 and∼ 0.16), which cannot be explained by the nearest-neighbor interaction proposed for the double-exchange mechanism. Instead, the collective effect of p-d hybridization and RKKY interaction of Pr 3+ f-electrons with the conduction electrons is suggested to be responsible for the long-range interaction. In addition, the discrepancy of β in the oxygen-stoichiometric Pr 0.5 Sr 0.5 CoO 3 may be due to a short-range interaction corresponding to the extra crystalline phases in the oxygen-stoichiometric sample.