Enhancement of giant magnetoresistance effect in the Ruddlesden–Popper phase Sr3Fe2−xCoxO7−δ: predominant role of oxygen nonstoichiometry and magnetic phase separation
Enhancement of giant magnetoresistance effect in the Ruddlesden–Popper phase Sr3Fe2−xCoxO7−δ: predominant role of oxygen nonstoichiometry and magnetic phase separation
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DOI：
10.1088/0953-8984/18/7/005
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发表时间：
2006-01
期刊：
影响因子：
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通讯作者：
Teruki Motohashi;B. Raveau;M. Hervieu;A. Maignan;V. Pralong;N. Nguyen;V. Caignaert
中科院分区：
文献类型：
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作者：
Teruki Motohashi;B. Raveau;M. Hervieu;A. Maignan;V. Pralong;N. Nguyen;V. Caignaert
系统地研究了Sr 3Fe 2 − xCoxO 7 −δ（0.2≤x≤1.0）系统的磁性和磁输运性质。该氧化物系统在低温下表现出巨磁电阻效应，在5 K下7 T下高达80%。交流磁化率测量表明，铁磁态（F）和自旋玻璃态（S）之间存在着强烈的竞争，通过改变Co（x）和/或O（δ）的含量，可以控制这两种磁态之间的平衡.重要的是，MR效应与磁性密切相关：磁无序的发展导致负MR效应的增强。这表明该化合物分离成嵌入非F基质中的F簇，是人工颗粒GMR材料的天然类似物，如掺杂的钙钛矿钴酸盐La 1 − xSrxCoO 3（x< 0.18）。
The magnetic and magnetotransport properties of the Sr3Fe2−xCoxO7−δ system (0.2≤x≤1.0) have been systematically investigated. This oxide system exhibits a giant magnetoresistance (GMR) effect at low temperatures, reaching up to 80% in 7 T at 5 K. Ac-susceptibility measurements show that there exists a strong competition between ferromagnetic (F) and spin glass states, and the balance between these two magnetic states can be controlled by varying cobalt (x) and/or oxygen contents (δ). Importantly, the MR effect is closely related to the magnetic property: the development of magnetic disordering leads to enhancement in the negative MR effect. It is suggested that the compound segregates into F clusters embedded in a non-F matrix, being a naturally occurring analogue of the artificial granular-GMR materials, as in the doped perovskite cobaltites, La1−xSrxCoO3 (x< 0.18).