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arXiv 2101.09804cond-mat.mtrl-sci
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Mg掺杂GaN附近（Ga，Mn）N薄膜的灵敏度积分SQUID磁学研究

Improved-Sensitivity Integral SQUID Magnetometry of (Ga,Mn)N Thin Films in Proximity to Mg-doped GaN

Katarzyna Gas, Gerd Kunert, Piotr Dluzewski, Rafal Jakiela, Detlef Hommel, Maciej Sawicki

备注：
16 pages, 6 figures
发表信息：
Journal of Alloys and Compounds 868, 159119 (2021)
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摘要：

采用分子束外延技术在GaN缓冲的Al 2 O3衬底上制备了45 nm GAN：Mg/ 5 nm（Ga，Mn）N / 45 nm GAN：Mg三层结构，以验证包层空穴的间接共掺杂是否会改变（Ga，Mn）N中的自旋-自旋相互作用.四个调查的结构，不同的镁掺杂水平，仔细表征在纳米级的HRTEM，EDX，和SIMS。HRTEM明确排除了外来富Mn相的存在。的结构，直到中等Mg掺杂，没有显示Mg过掺杂的影响。这些结构的磁性研究是由一个专门的实验方法的就业的辅助下，从基板的磁性贡献的原位补偿，允许高达约50倍的减少这种贡献。这种技术，致力于这些结构，同时提供了一个十倍减少的时间不稳定性的磁力单位，并降低了实验抖动，只有$5 \times 10^{-7}$ ~emu在70~kOe，大大提高了精度和可信度的结果，在高磁场的标准积分SQUID磁强计。本文所建立的三层结构的磁特性证明与厚的（Ga，Mn）N单层的已知性质相同，即（i）由超交换驱动的Mn $^{3+}$离子之间的低温铁磁性和（ii）在较高温度下的纯顺磁响应。缺乏由相邻Mg掺杂带来的任何影响的可能原因是包覆层中存在残余Mn，导致预期的p型掺杂在那里失活。这一发现指出，必须施加更密集的技术努力，以促进共掺杂驱动的载流子介导的铁磁耦合在Mn富集的GAN中，特别是在高温下。

英文摘要：

Nominally 45 nm GaN:Mg/ 5 nm (Ga,Mn)N / 45 nm GaN:Mg trilayers structures prepared by molecular beam epitaxy on GaN-buffered Al2O3 substrates are investigated to verify whether the indirect co-doping by holes from the cladding layers can alter the spin-spin interaction in (Ga,Mn)N. The four investigated structures, differing with the Mg doping level, are carefully characterized at the nanoscale by HRTEM, EDX, and by SIMS. HRTEM decisively excluded a presence of foreign Mn-rich phases. The structures, up to medium Mg doping, show no Mg over-doping effects. Magnetic studies of these structures are aided by the employment of a dedicated experimental approach of the in situ compensation of the magnetic contribution from the substrate, allowing up to about fifty-fold reduction of this contribution. This technique, dedicated to these structures, simultaneously provides a tenfold reduction of temporal instabilities of the magnetometric unit and lowers the experimental jitter to merely $5 \times 10^{-7}$~emu at 70~kOe, vastly increasing the precision and the credibility of the results of the standard integral SQUID magnetometry in high magnetic fields. The magnetic characteristics of the trilayers structures established here prove identical with the already known properties of the thick (Ga,Mn)N single layers, namely (i) the low temperature ferromagnetism among Mn$^{3+}$ ions driven by superexchange and (ii) purely paramagnetic response at higher temperatures. The possible cause of the lack of any effects brought about by the adjacent Mg-doping is a presence of residual Mn in the cladding layers, resulting in the deactivation of the p-type doping intended there. This finding points out that a more intensive technological effort has to be exerted to promote the co-doping-driven carrier-mediated ferromagnetic coupling in Mn-enriched GaN, especially at elevated temperatures.

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