The magnetocrystalline anisotropy of GdRh2Si2 is examined in detail via the electron spin resonance (ESR) of its well-localised Gd3+ moments. Below T N = 107 K, long range magnetic order sets in with ferromagnetic layers in the (aa)-plane stacked antiferromagnetically along the c-axis of the tetragonal structure. Interestingly, the easy-plane anisotropy allows for the observation of antiferromagnetic resonance at X- and Q-band microwave frequencies. In addition to the easy-plane anisotropy we have also quantified the weaker fourfold anisotropy within the easy plane. The obtained resonance fields are modelled in terms of eigenoscillations of the two antiferromagnetically coupled sublattices. Conversely, this model provides plots of the eigenfrequencies as a function of field and the specific anisotropy constants. Such calculations have rarely been done. Therefore our analysis is prototypical for other systems with fourfold in-plane anisotropy. It is demonstrated that the experimental in-plane ESR data may be crucial for a precise knowledge of the out-of-plane anisotropy.

中文翻译：

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GdRh2Si2 中的单轴和四重基础各向异性

通过其良好定位的 Gd3+ 矩的电子自旋共振 (ESR) 详细检查 GdRh2Si2 的磁晶各向异性。在 TN = 107 K 以下，长程磁序开始，(aa) 平面中的铁磁层沿四方结构的 c 轴反铁磁性堆叠。有趣的是，易平面各向异性允许在 X 和 Q 波段微波频率下观察反铁磁共振。除了易平面各向异性之外，我们还量化了易平面内较弱的四重各向异性。获得的共振场根据两个反铁磁耦​​合亚晶格的本征振荡建模。相反，该模型提供作为场和特定各向异性常数的函数的特征频率图。这种计算很少进行。因此，我们的分析对于具有四重面内各向异性的其他系统是典型的。结果表明，实验面内 ESR 数据可能对于准确了解面外各向异性至关重要。