论文标题
电荷密度调制和缺陷订购中的na $ _x $ mnbi $ _y $ ampainge semimetal
Charge Density Modulation and Defect Ordering in Na$_x$MnBi$_y$ magnetic semimetal
论文作者
论文摘要
I-MN-V抗铁磁铁Namnbi在2 K和9 t的晶体中产生了非常大的正磁性（MR），显示半导体到金属转变（SMT）。在没有SMT的情况下，获得了适度的（20％）MR。 Here, we show that upon cooling below the magnetic transition, a spatial modulation appears giving rise to new Bragg peaks due to charge and defect ordering in a checkerboard pattern, with two kinds of modulation vectors, $q_1$=($\frac23$, 0, 1) and $q_2$=($\frac23, \frac13, \frac12$).这构成了超晶格过渡（$ t_s $），可将对称性从高温中心对称P4/nmm到非中心对称P $ \ overline4 $ m2。在具有较大MR的晶体中，观察到接近室温$ T_S $，$ Q_1 $首先出现，其次是$ q_2 $。但是，在MR低的晶体中，$ T_S $要低得多，只观察到$ Q_1 $。电荷调制和自旋波动都可能有助于增强MR。
The I-Mn-V antiferromagnet, NaMnBi, develops a very large positive magnetoresistance (MR) up to 10,000% at 2 K and 9 T in crystals showing a semiconductor-to-metal transition (SMT). In the absence of an SMT, a modest (20%) MR is achieved. Here, we show that upon cooling below the magnetic transition, a spatial modulation appears giving rise to new Bragg peaks due to charge and defect ordering in a checkerboard pattern, with two kinds of modulation vectors, $q_1$=($\frac23$, 0, 1) and $q_2$=($\frac23, \frac13, \frac12$). This constitutes a superlattice transition ($T_s$) that lowers the symmetry from the high temperature centrosymmetric P4/nmm to the non-centrosymmetric P$\overline4$m2. In crystals with a large MR, a close to room temperature $T_s$ is observed with $q_1$ appearing first, followed by $q_2$. In crystals with low MR however, $T_s$ is much lower and only $q_1$ is observed. The charge modulation and spin fluctuations may both contribute to the enhancement of MR.
