Data associated with 'Effect of FePd alloy composition on the dynamics of artificial spin ice'

Artificial spin ices (ASI) are arrays of single domain nano-magnetic islands, arranged in geometries that give rise to frustrated magnetostatic interactions. It is possible to reach their ground state via thermal annealing. We have made square ASI using different FePd alloys to vary the magnetization via co-sputtering. From a polarized state the samples were incrementally heated and we measured the vertex population as a function of temperature using magnetic force microscopy. For the higher magnetization FePd sample, we report an onset of dynamics at $T = 493$ K, with a rapid collapse into $>90\%$ ground state vertices. In contrast, the low magnetization sample started to fluctuate at lower temperatures, $T = 393$ K and over a wider temperature range but only reached a maximum of $25\%$ of ground state vertices. These results indicate that the interaction strength, dynamic temperature range and pathways can be finely tuned using a simple co-sputtering process. In addition we have compared our experimental values of the blocking temperature to those predicted using the simple N\'{e}el-Brown two-state model and find a large discrepancy which we attribute to activation volumes much smaller than the island volume.

人工自旋冰（Artificial Spin Ices, ASI）是由单畴纳米磁岛构成的阵列，其几何排布会引发受挫静磁相互作用。该体系可通过热退火手段达到基态。本研究采用不同铁钯（FePd）合金体系，通过共溅射工艺调控磁化强度，制备得到方形人工自旋冰样品。将样品从极化态开始逐级升温，并借助磁力显微镜（Magnetic Force Microscopy, MFM）测量了顶点态占比随温度的变化关系。针对磁化强度更高的FePd样品，我们观测到其动力学过程起始温度为493 K，随后快速弛豫至占比超过90%的基态顶点构型。与之相对，低磁化强度样品在更低的393 K温度下即开始出现涨落，且对应的温度区间更广，但最终基态顶点占比仅达到25%。上述结果表明，通过简单的共溅射工艺即可精准调控相互作用强度、动力学温度区间及弛豫路径。此外，我们将实验测得的阻塞温度与基于简化奈尔-布朗两态模型的预测值进行了对比，发现二者存在显著偏差，我们将这一偏差归因于激活体积远小于纳米磁岛的实际体积。