We have compared the magnetic properties of well-controlled ultra-short (≤50 nm) atomic iron (Fe) chains embedded in Fe-phthalocyanine films with those in Fe–hydrogen (H2) phthalocyanine superlattices. Surprisingly, we found that the coercivity of the atomic chains with free boundary conditions is independent of the chain length, whereas the one subject to hybridization of the chain ends exhibits an unexpected length dependence. These findings suggest that ferromagnetism in the free-boundary condition system is caused by an intrinsic indirect exchange. On the other hand, controlled boundary conditions produce a helical spin structure due to an extrinsic indirect exchange, which arises from the interaction between iron atoms at the ends of the chain and the hydrogen in the H2 phthalocyanine spacer. As a consequence, during magnetic reversal, ultra-short iron chains subject to boundary clamping develop a helical spin structure, leading to increased coercivity. These findings suggest unique insights and ideas for the design of atomic-scale ultra-dense magnetic storage nanodevices.

中文翻译：

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具有杂化边界的铁链中的螺旋自旋结构

我们比较了嵌入 Fe-酞菁薄膜中的控制良好的超短 (≤50 nm) 原子铁 (Fe) 链的磁性与 Fe-氢 (H2) 酞菁超晶格中的磁性。令人惊讶的是，我们发现具有自由边界条件的原子链的矫顽力与链长无关，而链末端杂化的原子链表现出意想不到的长度依赖性。这些发现表明自由边界条件系统中的铁磁性是由内在的间接交换引起的。另一方面，受控边界条件由于外在间接交换而产生螺旋自旋结构，这是由链末端的铁原子与 H2 酞菁间隔中的氢之间的相互作用引起的。因此，在磁反转期间，受边界夹紧的超短铁链形成螺旋自旋结构，导致矫顽力增加。这些发现为设计原子级超密磁存储纳米器件提供了独特的见解和想法。