论文标题
A型Square-lattice抗Fiferromagnet EUGA $ _4 $的单晶中的低场磁异常
Low-field magnetic anomalies in single crystals of the A-type square-lattice antiferromagnet EuGa$_4$
论文作者
论文摘要
最近以身体为中心的四大抗铁磁铁EUGA $ _4 $最近被确定为一种Weyl节点线半含量，在其报告的抗铁磁性（AFM）订购温度$ t _ {\ rm n} = 15 $ -16.5 $ $ -16.5 k的情况下，表现出拓扑厅的效应（AFM）订购温度$ t _ {\ rm n}欧盟$^{+2} $离子位于单元单元的角落和车身中心。 EUGA $ _4 $在$ t _ {\ rm n} $下方展示A-Type AFM订单，其中eu $^{2+} $ spin-7/2时刻在$ ab $飞机上与欧洲eu矩阵中的EU eu Planes中的EU Moments在$ C $ C $ AXIS Antifififermagnet上与eu Planes中的EU时刻保持一致。据报道，在$ t = 2 $ k的$ t $ k的低场磁化与字段$ m（h_ {ab}）$数据据报道，在$ ab $平面中对齐的字段表现出异常的正曲率到关键场$ h_ {c1} $，二阶发生在$ h_ {c1} c1 {c1} \ 0.85 $ 0.85 $ koE的情况下， [1,1,0] $和$ \ $ \ 4.8 $ koe for $ {\ bf h} \ Parallel [1,0,0] $。对于较大的字段，线性行为$ m_ {ab} =χ（t _ {\ rm n}）h_ {ab} $一直遵循，直到先前报告的关键字段$ h^{\ rm c} _ {ab} _ {ab} = 71 $ koe与Applied Field均与Applied Field保持一致。一个理论是针对$ t = 0 $ k制定的，适合观察到的$ m（h_ {ab}）$行为在$ t = 2 $ k孔中，其中A-Type AFM订单的域具有四倍旋转对称性，在零字段的AFM状态发生。在$ h_ {c1} $上，四个领域中的矩几乎垂直于垂直于$ {\ bf h} _ {ab} $，随后将所有瞬间倾斜到田地上，随着范围的增加，最多增加了$ h^{\ rm c} _ {ab {ab} $。 $ h_ {ab} = h _ {\ rm c1} $在$ m（h_ {ab}）$中的一阶过渡是该理论的预测，当$ t = 0 $ k时，当$ {\ bf h} _ {ab {ab} $从[1,0,0]或[1,0,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1]时。
The body-centered-tetragonal antiferromagnet EuGa$_4$ was recently identified as a Weyl nodal-line semimetal that exhibits the topological Hall effect below its reported antiferromagnetic (AFM) ordering temperature $T_{\rm N}= 15$-16.5 K which we find to be $T_{\rm N} = 16.4(2)$ K. The Eu$^{+2}$ ions are located at the corners and body center of the unit cell. EuGa$_4$ exhibits A-type AFM order below $T_{\rm N}$, where the Eu$^{2+}$ spin-7/2 moments are ferromagnetically aligned in the $ab$ plane with the Eu moments in adjacent Eu planes along the $c$ axis aligned antiferromagnetically. Low-field magnetization versus field $M(H_{ab})$ data at $T=2$ K with the field aligned in the $ab$ plane are reported that exhibit anomalous positive curvature up to a critical field $H_{c1}$ at which a second-order transition occurs with $H_{c1}\approx 0.85$ kOe for ${\bf H}\parallel [1,1,0]$ and $\approx 4.8$ kOe for ${\bf H}\parallel [1,0,0]$. For larger fields, a linear behavior $M_{ab} = χ(T_{\rm N})H_{ab}$ is followed until the previously-reported critical field $H^{\rm c}_{ab} = 71$ kOe is reached at which all moments become aligned with the applied field. A theory is formulated for $T=0$ K that fits the observed $M(H_{ab})$ behavior at $T=2$ K well, where domains of A-type AFM order with fourfold rotational symmetry occur in the AFM state in zero field. The moments in the four domains reorient to become almost perpendicular to ${\bf H}_{ab}$ at $H_{c1}$, followed by increasing canting of all moments toward the field with increasing field up to $H^{\rm c}_{ab}$. A first-order transition in $M(H_{ab})$ at $H_{ab}=H_{\rm c1}$ is predicted by the theory for $T=0$ K when ${\bf H}_{ab}$ is at a small angle from the [1,0,0] or [1,1,0] directions.
