$YNi_2B_2C$和$LuNi_2B_2C$单晶中的磁通跳跃、第二磁化峰异常和峰效应现象
Flux jumps, Second Magnetization Peak anomaly and the Peak Effect phenomenon in single crystals of $YNi_2B_2C$ and $LuNi_2B_2C$
摘要：
本文报道了四元$YNi_2B_2C$化合物单晶的磁化强度测量结果，发现H $>$ 0.5T（H $||$ c）存在峰效应和第二磁化峰异常现象。在较低的磁场（50 mT $<$ H $<$ 200 mT）下，我们观察到了通量跳跃的存在，这似乎与通量线晶格的局部对称性的结构变化有关（在100 mT至150 mT的范围内，在样品的某些部分中的局部场上的一阶重取向转变）。这些通量跳跃也观察到在一个单一的晶体$LuNi_2B_2C$ H $||$ c的场区域从2 mT到25 mT，这是兼容的发生在一个较低的领域，在一个更干净的晶体，这种化合物，相比那些$YNi_2B_2C$的重取向转变。在$LuNi_2B_2C$和$YNi_2B_2C$中为H $||$ c绘制的涡旋相图表明，与后者相比，在前者中有序的弹性玻璃相跨越更大部分的（H，T）空间，从而重申了两种样品的相对纯度的差异。
英文摘要：
We present magnetization measurements in single crystals of the tetragonal $YNi_2B_2C$ compound, which exhibit the phenomenon of peak effect as well as the second magnetization peak anomaly for H $>$ 0.5T (H $||$ c). At the lower field (50mT $<$ H $<$ 200mT), we have observed the presence of flux jumps, which seem to relate to a structural change in the local symmetry of the flux line lattice (a first order re-orientation transition across a local field in some parts of the sample, in the range of 100mT to 150mT). These flux jumps are also observed in a single crystal of $LuNi_2B_2C$ for H $||$ c in the field region from 2 mT to 25 mT, which are compatible with the occurrence of a re-orientation transition at a lower field in a cleaner crystal of this compound, as compared to those of $YNi_2B_2C$. Vortex phase diagrams drawn for H $||$ c in $LuNi_2B_2C$ and $YNi_2B_2C$ show that the ordered elastic glass phase spans a larger part of (H, T) space in the former as compared to latter, thereby, reaffirming the difference in the relative purity of the two samples.
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