标题： 单晶ErB$_{2}$在低温下的易面铁磁性 显示英文标题

标题： Easy-plane ferromagnetism in single-crystal ErB$_{2}$ at low temperatures

摘要： 我们报告了通过自调节通量移动溶剂浮区技术制备的六方稀土二硼化物ErB$_{2}$单晶的研究。磁化率、交流磁化率、比热和电阻率的测量一致表明，在约$T_{c} = 14$K 的二级相变以下，Er$^{3+}$磁矩出现铁磁有序，并具有非常强的易平面各向异性。交流磁化率的居里-韦斯拟合表现出易六方基面上的铁磁耦合以及沿$\langle001\rangle$的反铁磁耦合。在基面内的磁场下，磁化率类似于软铁磁体，在几十分之一特斯拉以上的场中被极化，磁滞几乎消失且面内各向异性可忽略。在沿$\langle001\rangle$的磁场下，观察到典型的硬轴行为，磁化率仅在自旋翻转转变发生在$\mu_{0}H_{c} = 12$~T 时才略有增加。易平面各向异性在交叉温度$T_{x} \approx 50$~K 以下出现，即 一个高于$T_{c}$的广泛顺磁温度范围由强各向异性的磁涨落所支配。 显示英文摘要

摘要： We report a study of single crystals of the hexagonal rare-earth diboride ErB$_{2}$ prepared by means of the self-adjusted flux travelling-solvent floating-zone technique. Measurements of the magnetization, ac susceptibility, specific heat, and electrical resistivity consistently establish ferromagnetic order of the Er$^{3+}$ moments below a second-order phase transition at $T_{c} = 14$~K and a very strong easy-plane anisotropy. Curie--Weiss fits of the ac susceptibility are characteristic of ferromagnetic coupling within the easy hexagonal basal plane, and antiferromagnetic coupling along $\langle001\rangle$. Under magnetic field within the basal plane the magnetization is reminiscent of a soft ferromagnet that is polarized in fields above a few tenth of a Tesla, vanishing hysteresis and negligible in-plane anisotropy. Under field along $\langle001\rangle$, typical hard-axis behavior is observed with the magnetization increasing only weakly up to a spin-flip transition at $\mu_{0}H_{c} = 12$~T. The easy-plane anisotropy emerges below a crossover temperature $T_{x} \approx 50$~K , i.e. a broad paramagnetic temperature range above $T_{c}$ is governed by strongly anisotropic magnetic fluctuations.