标题： 多形态ErAl3的各向异性磁性 显示英文标题

标题： Anisotropic magnetism of polymorphic ErAl3

摘要： ErAl$_3$可以形成三棱柱（$\alpha$）或立方（$\beta$）多形，并且本文通过在铝熔融物中生长的单晶表征来研究这些多形的物理性质。 我们证明可以根据晶体生长的名义组成实现多形选择。 磁性测量证实，$\beta$-ErAl$_3$和$\alpha$-ErAl$_3$在低温下均反铁磁有序。 $\beta$-ErAl$_3$在奈尔温度 T$_N$ = 5.1 K 下发生反铁磁有序，且该转变在施加磁场时持续被抑制。$\alpha$-ErAl$_3$表现出更复杂的行为，在零场下依次在 T$_N$ = 5.7 K 和 T$_2$ = 4.6 K 发生磁性转变，其中比热和膨胀计测量表明这些转变分别为二阶和一阶。 在磁场下，$\alpha$-ErAl$_3$显示出强烈的各向异性，在T$_2$以下对于H$\parallel$c观察到几个类似台阶的磁致相变。这些相变在表观饱和磁化强度的一半附近产生连续的磁化平台。 $\alpha$-ErAl$_3$的电阻率与其磁性强烈耦合。 在$T$ = 2 K时，我们观察到正磁阻效应达到60%，并在磁致相变处出现明显的异常。 结果在$H$-$T$相图中总结，这些相图展示了$\alpha$-ErAl$_3$的复杂磁行为，表明在具有伊辛物理特性的金属系统中，竞争相互作用起着重要作用。 显示英文摘要

摘要： ErAl$_3$ can form in either a trigonal ($\alpha$) or cubic ($\beta$) polymorph and this paper investigates the physical properties of these polymorphs through characterizations of single crystals grown in an aluminum flux. We demonstrate that polymorph selection can be achieved based on the nominal composition of the crystal growth. Magnetic measurements confirm that both $\beta$-ErAl$_3$ and $\alpha$-ErAl$_3$ order antiferromagnetically at low temperatures. $\beta$-ErAl$_3$ undergoes AFM ordering at a N\'eel temperature T$_N$ = 5.1 K, and the transition is suppressed continually with applied field. $\alpha$-ErAl$_3$ displays more complex behavior, with successive magnetic transitions at T$_N$ = 5.7 K and T$_2$ = 4.6 K for zero field, where heat capacity and dilatometry measurements evidence that these transitions are second- and first-order, respectively. Under magnetic field, strong anisotropy is revealed in $\alpha$-ErAl$_3$, with several step-like metamagnetic transitions observed below T$_2$ for H$\parallel$c. These transitions produce sequential magnetization plateaus near one-half of the apparent saturation magnetization. The electrical resistivity of $\alpha$-ErAl$_3$ is strongly coupled to its magnetism. At $T$ = 2 K, we observe a positive magnetoresistance reaching 60\%, with distinct anomalies at the metamagnetic transitions. The results are summarized in $H$- $T$ phase diagrams that demonstrate complex magnetic behavior for $\alpha$-ErAl$_3$, suggesting an important role of competing interactions in this metallic system that possesses characteristics of Ising physics.