（Ga，Mn）As铁磁性与局域化相互作用的实验研究
Experimental probing of the interplay between ferromagnetism and localisation in (Ga,Mn)As
摘要：
安德森-莫特局域化是增强还是减弱磁相关性的问题是磁性合金物理学的核心。特别有趣的是（Ga，Mn）As和相关的磁性半导体的情况下，已经提出了不同的理论方案。在这里，通过直接磁化测量，我们演示了磁性如何演变时，介导的自旋-自旋耦合的载流子的密度减少的栅极电场在金属/绝缘体/半导体结构的（Ga，Mn）As。我们的研究结果表明，沟道耗尽的居里温度的单调下降的结果，没有证据的杂质带模型内预期的最大值。我们发现，从铁磁到顺磁状态的过渡收益通过出现超顺磁性的自旋排列。这意味着载流子局域化导致相分离成铁磁和非铁磁区域，我们将其归因于局部态密度的临界波动，具体到安德森-莫特量子跃迁。
英文摘要：
The question whether the Anderson-Mott localisation enhances or reduces magnetic correlations is central to the physics of magnetic alloys. Particularly intriguing is the case of (Ga,Mn)As and related magnetic semiconductors, for which diverging theoretical scenarios have been proposed. Here, by direct magnetisation measurements we demonstrate how magnetism evolves when the density of carriers mediating the spin-spin coupling is diminished by the gate electric field in metal/insulator/semiconductor structures of (Ga,Mn)As. Our findings show that the channel depletion results in a monotonic decrease of the Curie temperature, with no evidence for the maximum expected within the impurity-band models. We find that the transition from the ferromagnetic to the paramagnetic state proceeds via the emergence of a superparamagnetic-like spin arrangement. This implies that carrier localisation leads to a phase separation into ferromagnetic and nonmagnetic regions, which we attribute to critical fluctuations in the local density of states, specific to the Anderson-Mott quantum transition.
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