Phase Transition from Antiferromagnetic Insulator to Ferromagnetic Metal in La2-xSrxCoO4 –Magnetization and NMR Studies–
Phase Transition from Antiferromagnetic Insulator to Ferromagnetic Metal in La2-xSrxCoO4 –Magnetization and NMR Studies–
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DOI：
10.1143/jpsj.62.1127
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发表时间：
1993-04
影响因子：
1.7
通讯作者：
Y. Furukawa;S. Wada;Yoshihiro Yamada
中科院分区：
文献类型：
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作者：
Y. Furukawa;S. Wada;Yoshihiro Yamada
对超导铜酸盐的同晶化合物之一La 2- x Sr x CoO 4 体系( x =0–1.4) 进行了磁和零场核磁共振研究。在富La区域（x≤0.5），反铁磁（AF）有序性仍然存在，并且1.4K时的内部磁场几乎保持恒定（Hint（Co）≃200kOe），尽管尼尔温度随着少量Sr的取代而显示出最初的强烈下降。当x进一步增加（x≥0.6）时，AF态突然转变为铁磁态，居里温度在x=0.9处显示最大值（TC=220K）。然而，T = 4.2 K 时的自发磁化强度仅在 x = 0.7–0.9 范围内非零 (2.2–1.6 µ B )，并且 H int (Co) 从 190 kOe ( x = 0.6) 急剧下降到 40 kOe ( x = 1.1) 以下。 x =0.7和0.9时59 Co自旋晶格弛豫时间T 1 遵循关系式T 1 T = const.，表明它处于金属态。
Magnetic and zero-field nuclear magnetic resonance investigations have been made on the La 2- x Sr x CoO 4 system ( x =0–1.4), one of the isomorphous compounds of the superconducting cuprates. In the La-rich region ( x ≤0.5), the antiferromagnetic (AF) ordering persists and the internal magnetic field at 1.4 K remains almost constant ( H int ( Co)≃200 kOe), though the Neel temperature shows an initial strong decrease with a small amount of Sr substitution. When x increases further ( x ≥0.6), the AF state suddenly transforms to a ferromagnetic state and the Curie temperature shows a maximum ( T C =220 K) at x =0.9. Spontaneous magnetizations at T =4.2 K are, however, non-zero (2.2–1.6 µ B ) only in the range of x =0.7–0.9, and H int ( Co) strongly decreases from 190 kOe ( x =0.6) to below 40 kOe ( x =1.1). 59 Co spin-lattice relaxation time T 1 for x =0.7 and 0.9 follows the relation T 1 T =const., suggesting it is in a metallic state.