Ferromagnetic Quantum Criticality Studied by Hall Effect Measurements in UCoAl
Ferromagnetic Quantum Criticality Studied by Hall Effect Measurements in UCoAl
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DOI：
10.7566/jpsj.82.104705
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发表时间：
2013-10-01
影响因子：
1.7
通讯作者：
Flouquet, Jacques
中科院分区：
文献类型：
--
作者：
Combier, Tristan;Aoki, Dai;Flouquet, Jacques
在2.2GPa和16 T的压力和磁场下对UCoAl单晶进行了霍尔效应测量。在常压下，系统在临界场B-m = 0：7 T下发生了从顺磁基态到场致铁磁态的一级变磁转变.霍尔信号在低场下呈线性，在过渡区呈现台阶状异常，霍尔系数变化不大。在临界端点T-0 = 12 K处异常最明显，在此温度以上，一级变磁转变变为交叉。在压力下，B-m增加，T-0减小。当P-M接近1：3GPa时，霍尔效应的台阶状异常消失，当P-Delta接近1：7 GPa，B-m接近7 T时，在量子临界点以上没有检测到变磁跃迁。使用磁化数据，我们分析了我们的霍尔电阻率数据在环境压力下，以定量占普通和异常的霍尔效应的贡献。在压力下，霍尔系数的场依赖性的急剧变化被发现跨越QCEP。一个可能的费米面在B-m的变化仍然是一个悬而未决的问题。
Hall effect measurements were performed under pressure and magnetic field up to 2.2 GPa and 16 T on a single crystal of UCoAl. At ambient pressure, the system undergoes a first order metamagnetic transition at the critical field B-m = 0: 7 T from a paramagnetic ground state to a field-induced ferromagnetic state. The Hall signal is linear at low field and shows a step-like anomaly at the transition, with only little change of the Hall coefficient. The anomaly is sharpest at the temperature of the critical end point T-0 = 12K above which the first order metamagnetic transition becomes a crossover. Under pressure B-m increases and T-0 decreases. The step-like anomaly in the Hall effect disappears at P-M approximate to 1: 3 GPa and the metamagnetic transition is not detected above the quantum critical end point (QCEP) at P-Delta approximate to 1: 7 GPa, B-m approximate to 7 T. Using magnetization data, we analyse our Hall resistivity data at ambient pressure in order to quantitatively account for both ordinary and anomalous contributions to the Hall effect. Under pressure, a drastic change in the field dependence of the Hall coefficient is found on crossing the QCEP. A possible Fermi surface change at B-m remains an open question.