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首页> 外文期刊>Physical review >Pressure-induced quantum phase transition in Fe_(1-x)Co_xSi (x = 0.1,0.2)
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Pressure-induced quantum phase transition in Fe_(1-x)Co_xSi (x = 0.1,0.2)

机译：Fe_（1-x）Co_xSi（x = 0.1,0.2）中的压力诱导量子相变

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We have investigated the effect of pressure on electrical transport and magnetic properties of ferromagnetic Fe_(1-x)Si alloys for x = 0.1 (T_c ～ 11 K) and x= 0.2 (T_c ～ 32 K) using electrical resistivity measurements up to about 30 GPa. We have also studied the magnetic properties of these samples (x = 0.1 and x =0.2) and a sample with x = 0.3 (T_C～ 43 K) at ambient pressure using ~(57)Fe Moessbauer-effect (ME) spectroscopy. The ME results indicate that the effective magnetic hyperfine field 5_(eff)at the ~(57)Fe nucleus exhibits the same concentration dependence as the macroscopic magnetic moment and confirm that the onset of magnetic order is above x～ 0.02. The analysis of the high-pressure results reveals in both samples a gradual suppression of the ferromagnetic state to a quantum phase transition (QPT) at pressures of p～11 GPa and p ～12 GPa for x = 0.1 and x = 0.2, respectively. High-pressure x-ray diffraction measurements on the three samples indicate very similar change of the volume of the cubic unit cell with pressure and exclude that the observed QPTs are connected with a structural phase transition. We discuss the observed instability of the ferromagnetic state with increasing Co concentration in the context of increasing local crystallographic disorder, which causes a change of the distribution of the helix wave vector as well as a modification of the ferromagnetic half-metallic state. We further show that, in the pressure-induced nonmagnetic metallic state, all samples, regardless of their different local crystallographic disorder, exhibit similar non-Fermi-liquid behavior [ρ(T)α T]. Finally, we find a small but positive magnetoresistance in the high-pressure metallic state well beyond the QPT of Fe_(0.9)Co_(0.1) Si. This can be attributed to a slight field-induced modification of the spin majority and minority band which leads to a very small magnetic moment.
机译：我们使用电阻率测量值直至x = 0.1（T_c〜11 K）和x = 0.2（T_c〜32 K）研究了压力对铁磁Fe_（1-x）Si合金的电输运和磁性能的影响。 30 GPa。我们还使用〜（57）Fe莫斯鲍尔效应（ME）光谱研究了这些样品（x = 0.1和x = 0.2）和x = 0.3（T_C〜43 K）在环境压力下的磁性。磁电学结果表明，〜（57）Fe原子核上的有效磁超精细场5_（eff）表现出与宏观磁矩相同的浓度依赖性，并证实了磁序的开始在x〜0.02以上。高压结果的分析表明，在两个样品中，当x = 0.1和x = 0.2时，在p〜11 GPa和p〜12 GPa的压力下，铁磁态逐渐抑制为量子相变（QPT）。对三个样品进行的高压X射线衍射测量表明，立方晶胞的体积随压力变化非常相似，并且排除了观察到的QPT与结构相变有关。我们讨论了在局部结晶学无序增加的情况下，随着Co浓度的增加，铁磁态的不稳定性，这会导致螺旋波矢分布的变化以及铁磁半金属态的改变。我们进一步表明，在压力诱导的非磁性金属状态下，所有样品，无论其不同的局部晶体学紊乱如何，均表现出相似的非费米液体行为[ρ（T）αT]。最后，我们在高压金属状态下发现了一个很小的正磁阻，远超过了Fe_（0.9）Co_（0.1）Si的QPT。这可以归因于场的自旋多数和少数能带的轻微改变，这导致很小的磁矩。

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