Huge anisotropic magnetostriction in La 1-x Sr x CoO 3-δ (x>=0.3): Field-induced orbital instability
Huge anisotropic magnetostriction in La 1-x Sr x CoO 3-δ (x>=0.3): Field-induced orbital instability
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La 1-x Sr x CoO 3-δ (x>=0.3) 中巨大的各向异性磁致伸缩：场致轨道不稳定
DOI：
10.1103/physrevb.57.r3217
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发表时间：
1998
影响因子：
3.7
通讯作者：
J. Blasco
中科院分区：
文献类型：
--
作者：
M. R. Ibarra;R. Mahendiran;C. Marquina;B. García;J. Blasco
测量了与外加磁场平行和垂直的磁致伸缩${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{CoO}}_{3}$$(x=0.3，在很宽的温度范围$(4.2l~Tl~300$K)和高达14.2T的最大磁场范围内，我们发现了一个巨大的各向异性磁致伸缩$({\ensureath{\lambda}}_{t})$，其值在$x=0.3$时为$2.2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$，在$x=0.5$时为$1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$当温度低于100K时，体积磁致伸缩可以忽略不计。大的值不能用通常的自旋-轨道耦合贡献来解释。我们认为，这种巨大的各向异性磁致伸缩源于三价钴离子在磁场作用下的轨道不稳定性，导致了从非简并的低自旋态到轨道简并的中间自旋态的跃迁。
Magnetostriction parallel and perpendicular to the applied magnetic field has been measured for ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{CoO}}_{3}$ $(x=0.3, 0.5)$ over a wide temperature range $(4.2l~Tl~300$ K) and up to a maximum field of 14.2 T. We find a huge anisotropic magnetostriction $({\ensuremath{\lambda}}_{t})$ with values as large as $2.2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$ for $x=0.3$ and $1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$ for $x=0.5$ at 14.2 T and temperatures below 100 K. The volume magnetostriction has been found to be negligible. The large value of ${\ensuremath{\lambda}}_{t}$ cannot be explained on the basis of the usual spin-orbit-coupling contribution. We propose that such a huge anisotropic magnetostriction has its origin in the orbital instability of the trivalent Co ions under the magnetic field, giving rise to a transition from a nondegenerated low-spin state to an orbital degenerated intermediate-spin state.