不同磁场值下样品specific-heat曲线中的特征交叉点（$T_{\ast}\approx 2.7$ K）RuSr PDMATHAAD Gd PDMATHAAE Ce $_{0.5}$ Cu $_2$ O $_{10-δ}$
Characteristic crossing point ($T_{\ast}\approx 2.7$ K) in specific-heat curves of samples RuSr$_2$Gd$_{1.5}$Ce$_{0.5}$Cu$_2$O$_{10-δ}$ taken for different values of magnetic field
摘要：
本文报道了RuSr $_2$（Gd $_{1.5}$ Ce $_{0.5}$）Cu $_{2}$ O $_{10-δ}$多晶样品的磁性能，这些样品是用固相反应法制备的，并在不同压力（30、62和78 atm）的纯氧中退火（845 $^{\circ}$ C，12小时）。在1.8- 300 K温度范围内，在磁场高达8 T的条件下，研究了样品的比热和磁化强度。比热，$C(T)$，显示了超导转变的跳跃（在$T\approx 37.5$ K开始）。低于20 K，肖特基型异常在$C(T)$中变得明显。这种低温异常可以归因于内部和外部磁场的顺磁Gd $^{3+}$离子的地面项${^8}S_{7/2}$分裂。发现对于所研究的所有样品，在不同磁场值下所取的曲线$C(T)$具有相同的交叉点（在$T_{\ast}\approx 2.7$ K处）。同时，对于不同温度所取的$C(H)$曲线在特征场$H_{\ast}\approx 3.7$ T处具有交叉点。这些效应可以被认为是交叉点现象的表现，这应该是强关联电子系统所固有的。
英文摘要：
Magnetic properties of polycrystalline samples of RuSr$_2$(Gd$_{1.5}$Ce$_{0.5}$)Cu$_{2}$O$_{10-δ}$, as-prepared (by solid-state reaction) and annealed (12 hours at 845$^{\circ}$C) in pure oxygen at different pressure (30, 62 and 78 atm) are presented. Specific heat and magnetization were investigated in the temperature range 1.8--300 K with a magnetic field up to 8 T. Specific heat, $C(T)$, shows a jump at the superconducting transition (with onset at $T\approx 37.5$ K). Below 20 K, a Schottky-type anomaly becomes apparent in $C(T)$. This low-temperature anomaly can be attributed to splitting of the ground term ${^8}S_{7/2}$ of paramagnetic Gd$^{3+}$ ions by internal and external magnetic fields. It is found that curves $C(T)$ taken for different values of magnetic field have the same crossing point (at $T_{\ast}\approx 2.7$ K) for all samples studied. At the same time, $C(H)$ curves taken for different temperatures have a crossing point at a characteristic field $H_{\ast}\approx 3.7$ T. These effects can be considered as manifestation of the crossing-point phenomenon which is supposed to be inherent for strongly correlated electron systems.
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