We explore the exchange bias coupling at the RE-RE interfaces (RE denotes rare earth) due to a plausible increase in the spin-imbalance induced by magnetic sublattice disorder around the temperature range where one of the REs exists in its conical phase while the other remains ferromagnetic (FM). In this regard, two highly textured multilayers with 29 monolayers (ML) of Ho are grown, which interface with 7 and 21 ML of Tb. For ${\mathrm{ML}}_{\mathrm{Tb}}=7$, the noncollinear spin configuration constituting a fraction of the whole stack regulates the effect of the surface-area-to-volume ratio as the helix usually remains truncated, while for ${\mathrm{ML}}_{\mathrm{Tb}}=21$, the helix can be sufficiently profound. Both samples exhibit at least two temperature-dependent phases of the spin configuration of Ho: conical and helical. For the ${\mathrm{ML}}_{\mathrm{Tb}}=7$ sample, significant exchange bias fields of up to $-0.57\pm 0.1\mathrm{kOe}$ are observed along with double hysteresis loops (DHLs) below 20 K. For ${\mathrm{ML}}_{\mathrm{Tb}}=21$, the coupling strength diminishes to $-0.055\pm 0.01\mathrm{kOe}$ as we also find shifts in the temperature behavior regimes related to the conical-to-helical and helical-to-paramagnetic phase fractions within Ho. This emblemizes the effect of helical phase formation in Tb on the Ho spin configuration. Instead of nanoclustering, regular FM behavior is seen around the temperature range of conical-to-helical phase evolution. As we replace 21 ML of Tb with 10 ML of a ferromagnet (CoFe), we find the usual DHLs and an exchange bias field up to $-0.02\pm 0.01\mathrm{kOe}$. The exchange bias phenomenon in Ho/Tb multilayer below 20 K is attributed to the small spin imbalance in the magnetic sublattice disorders in the conical phase of Ho.

中文翻译：

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由于 Ho 磁性亚晶格无序而导致 Ho/Tb 多层内 Ho 锥形相的交换耦合

我们探索了 RE-RE 界面（RE 表示稀土）的交换偏置耦合，这是由于在其中一个 RE 存在于其锥形相而另一个 RE 存在的温度范围附近，磁性亚晶格无序引起的自旋不平衡可能增加。仍然是铁磁 (FM)。在这方面，生长了两个具有 29 个单层 (ML) Ho 的高度织构多层，它们与 7 和 21 ML Tb 界面。为了${\mathrm{机器学习}}_{铽}=7$，构成整个堆栈一部分的非共线自旋构型调节表面积与体积比的影响，因为螺旋通常保持截断，而对于${\mathrm{机器学习}}_{铽}=21$，螺旋可以足够深。两个样品都表现出至少两个与温度相关的 Ho 自旋构型：圆锥形和螺旋形。为了${\mathrm{机器学习}}_{铽}=7$样本，显着的交换偏差场高达$-0.57\pm 0.1\mathrm{科埃}$与低于 20 K 的双磁滞回线 (DHL) 一起观察到。${\mathrm{机器学习}}_{铽}=21$，耦合强度减小到$-0.055\pm 0.01\mathrm{科埃}$因为我们还发现与 Ho 内圆锥形到螺旋形和螺旋形到顺磁相分数相关的温度行为范围的变化。这象征着 Tb 中螺旋相的形成对 Ho 自旋构型的影响。在圆锥形到螺旋形相演化的温度范围内观察到规则的 FM 行为，而不是纳米团簇。当我们用 10 ML 的铁磁体 (CoFe) 替换 21 ML 的 Tb 时，我们发现通常的 DHL 和交换偏置场高达$-0.02\pm 0.01\mathrm{科埃}$。 Ho/Tb多层中低于20 K的交换偏压现象归因于Ho圆锥相中磁性亚晶格无序中的小自旋不平衡。