标题： 铁磁量子临界点附近的磁序和自旋动力学在Ni\boldmath{$_{1-x}$}Mo\boldmath{$_{x}$} 显示英文标题

标题： Magnetic order and spin dynamics across the ferromagnetic quantum critical point in Ni\boldmath{$_{1-x}$}Mo\boldmath{$_{x}$}

摘要： 在纯净的铁磁金属中实现量子临界点（QCP）一直是一个难题，这是由于磁化强度与驱动相变的电子软模之间的耦合导致相变成为一级相变。 然而，通过引入适量的静态无序，仍然可以在铁磁体中建立QCP。 在本研究中，我们确定巡游铁磁体Ni$_{1-x}$Mo$_{x}$在临界掺杂量$x_c \simeq 0.125$处表现出FM QCP。 通过磁化和穆斯鲍尔谱测量，我们证明FM有序温度在$x_c$处连续降低到零，而磁性体积分数在$x_c$之前保持$100\%$，表明这是一个二阶相变。 QCP伴随着非费米液体行为，这由比热的对数发散和低温电阻率的线性温度依赖性所证实。 我们的研究结果揭示了无序对Ni$_{1-x}$Mo$_{x}$在$x_c$时临界自旋动力学的最小影响，突显了它作为少数表现出纯净铁磁QCP的系统之一。 显示英文摘要

摘要： Realizing a quantum critical point (QCP) in clean ferromagnetic (FM) metals has remained elusive due to the coupling of magnetization to the electronic soft modes that drive the transition to be of first order. However, by introducing a suitable amount of quenched disorder, one can still establish a QCP in ferromagnets. In this study, we ascertain that the itinerant ferromagnet Ni$_{1-x}$Mo$_{x}$ exhibits a FM QCP at a critical doping of $x_c \simeq 0.125$. Through magnetization and muon-spin relaxation measurements, we demonstrate that the FM ordering temperature is suppressed continuously to zero at $x_c$, while the magnetic volume fraction remains $100\%$ up to $x_c$, indicating a second-order phase transition. The QCP is accompanied by a non-Fermi liquid behavior, as evidenced by the logarithmic divergence of the specific heat and the linear temperature dependence of the low-temperature resistivity. Our findings reveal a minimal effect of disorder on the critical spin dynamics of Ni$_{1-x}$Mo$_{x}$ at $x_c$, highlighting it as one of the rare systems to exhibit a clean FM QCP.