Magnetic phases of ultrathin Fe grown on Cu(100) as epitaxial wedges

Li, Dongqi; Freitag, M.; Pearson, John; Qiu, Z. Q.; Bader, S. D.

doi:10.1103/physrevlett.72.3112

Cited by 337 publications

(228 citation statements)

References 35 publications

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“…Concluding this brief structural survey, we find that while all structures are fairly similar, the films around 3.0 ML, which showed high magnetization in previous studies [1,12,13], have the highest bcc-like content and form the widest bcc-like stripes, whereas the films close to 2 and 5 ML show more narrow bcc-like stripes and high fcc content, respectively, which indicates a clear correlation of the bcc-like structure and the magnetization. The characteristic twin structure of these zigzaglike bcc phases combines local bcc order with a good lattice matching at the fcc substrate interface and a masstransfer-free fcc-bcc transition pathway, the hallmarks of bulk martensitic transitions (see, e.g., Ref.…”

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confidence: 85%

“…Imaging was done using either a room temperature scanning tunneling microscope (STM) or a low temperature STM operated at 80 K with in situ sputtered W tips. Ion scattering experiments show that the surfaces of films more than 3 ML thick deposited at room temperature contain less than a few percent copper [10].Before we report on the atomic structure of the films, a general remark: It is well known from previous experiments that the atomic structure can change within fractions of a monolayer and also with temperature [1,11].Since it is very difficult to obtain atomic resolution on these surfaces, we did not attempt to outline the boundaries in the phase diagram by STM, which has been done before by means of LEED and the surface magnetooptical Kerr effect [1,12,13], but rather focused on the principal structures and driving forces, which support ferromagnetism in the 2-4 ML films. …”

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confidence: 99%

“…Since it is very difficult to obtain atomic resolution on these surfaces, we did not attempt to outline the boundaries in the phase diagram by STM, which has been done before by means of LEED and the surface magnetooptical Kerr effect [1,12,13], but rather focused on the principal structures and driving forces, which support ferromagnetism in the 2-4 ML films.…”

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Crystallographic Structure of Ultrathin Fe Films on Cu(100)

et al. 2001

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We report bcc-like crystal structures in 2-4 ML Fe films grown on fcc Cu(100) using scanning tunneling microscopy. The local bcc structure provides a straightforward explanation for their frequently reported outstanding magnetic properties, i.e., ferromagnetic ordering in all layers with a Curie temperature above 300 K. The non-pseudomorphic structure, which becomes pseudomorphic above 4 ML film thickness is unexpected in terms of conventional rules of thin film growth and stresses the importance of finite thickness effects in ferromagnetic ultrathin films.Both academic interest in novel nanomagnetic phenomena as well as their technological importance for magneto-electronics and high density magnetic storage devices make the study of ultrathin ferromagnetic films particularly worthwhile. These extremely thin films, typically less than 10 monolayers (ML) thick, exhibit significantly different magnetic properties in contrast to the bulk material, e.g., different magnetization directions, enhanced magnetic moments, and lower Curie temperatures. Fe films epitaxially grown on Cu(100) are distinguished by a particular complex behavior since they are variable both with respect to magnetic ordering (ferroor antiferromagnetic) and crystal structure (fcc or bcc). Although the epitaxial system Fe/Cu(100) is under intense scrutiny for more than a decade and its magnetic properties have been mapped very precisely, no conclusive overall picture of the relation between structure and magnetic states has emerged yet. Regarding the model for films deposited at room temperature presently discussed in the literature, there is clear evidence for an antiferromagnetic, pseudomorphic fcc phase between 5 and 10 ML film thickness. The character and origin of the ferromagnetic phase between 2 and 4 ML, however, remains unclear. Low energy electron diffraction (LEED) [1], surface extended X-ray absorption fine-structure (SEXAFS) [2], and medium energy ion scattering studies (MEIS) [3] indicate a distinct distortion of the fcc lattice in 2-4 ML films. This reconstruction, which is considered to comprise the entire film thickness [1], is accompanied by a substantial increase of the film volume (interlayer distance) by about 5% [1,4]. In the past, these results led to the notion of a second, ferromagnetic fcc-like phase with an expanded film volume, i.e., a face centered tetragonal (fct) phase. While ab-initio calculations of bulk Fe do support the possibility of a ferromagnetic fcc phase with expanded volume under substantial tensile strain [5], the respective calculations of ultrathin films on Cu(100) did not provide an unambiguous confirmation of the ferromagnetic fct model [6,7]. This is an important question since the hypothetical existence of a ferromagnetic fcc-like phase is relevant also for the solid state physics of Fe. The two-γ-state model introduced by Kaufman, Clougherty, and Weiss [8], assuming two fcc states of bulk Fe either ferro-or antiferromagnetic, is still under discussion.In this Letter, we resolve this issue by char...

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Crystallographic Structure of Ultrathin Fe Films on Cu(100)

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“…This is also corroborated by the prediction of an SH in free-standing monolayers (MLs) of bcc-Fe(110) in theory 12 . In view of a change of spin order, driven by subtle structural changes, the Fe/Cu(001) system is a prototypical example for extended Fe layers [22][23][24] . We exploit that Fe in bridge-site-stacking is stabilized only in nm-small BLr Fe islands on Cu(111), which plays a pivotal role of the formation of the SH reported here.…”

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Reduced-dimensionality-induced helimagnetism in iron nanoislands

et al. 2014

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Low-dimensionality in magnetic materials often leads to noncollinear magnetic order, such as a helical spin order and skyrmions, which have received much attention because of envisioned applications in spin transport and in future data storage. Up to now, however, the real-space observation of the noncollinear magnetic order has been limited mostly to systems involving a strong spin-orbit interaction. Here we report a noncollinear magnetic order in individual nanostructures of a prototypical magnetic material, bilayer iron islands on Cu (111). Spin-polarized scanning tunnelling microscopy reveals a magnetic stripe phase with a period of 1.28 nm, which is identified as a one-dimensional helical spin order. Ab initio calculations identify reduced-dimensionality-enhanced long-range antiferromagnetic interactions as the driving force of this spin order. Our findings point at the potential of nanostructured magnets as a new experimental arena of noncollinear magnetic order stabilized in a nanostructure, magnetically decoupled from the substrate.

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“…Fe and Cr multilayer with body centered cubic (bcc) lattice is well known as the typical system for giant magnetoresistance (GMR) device, showing an in-plane magnetic anisotropy and an oscillatory interlayer magnetic coupling [1][2][3][4]. In contrast to this, Fe films with face centered cubic (fcc) lattice can be stabilized on Cu(001) substrate [5][6][7][8][9][10][11][12]. Up to 4 monolayer (ML), corresponding to the thinnest thickness region of Fe ("region I Fe " hereafter), the films show the face-centered-tetragonal (fct) structure elongated out-of-plane direction and exhibits out-of-plane magnetic anisotropy.…”

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confidence: 94%

Growth Mode and Surface Structure of Cr Ultrathin Film on Fe/Cu(001)

Tohoda

Nagira

Ueno

et al. 2008

e-J. Surf. Sci. Nanotechnol.

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We hereby report a growth mode and surface structure of ultrathin Cr films on fcc Fe/Cu(001). We have found a clear RHEED intensity oscillation during Cr deposition up to four monolayers on 3 and 6 ML Fe/Cu(001), indicating an layer-by-layer growth. Besides, the observed (2×1) LEED pattern at low Cr thickness is similar to that of fcc Fe/Cu(001) in the 5-11 ML thickness range. We have also demonstrated the Cr/Fe multilayer growth with single monolayer of Cr inserted between fcc Fe layers.

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Magnetic phases of ultrathin Fe grown on Cu(100) as epitaxial wedges

Cited by 337 publications

References 35 publications

Crystallographic Structure of Ultrathin Fe Films on Cu(100)

Crystallographic Structure of Ultrathin Fe Films on Cu(100)

Reduced-dimensionality-induced helimagnetism in iron nanoislands

Growth Mode and Surface Structure of Cr Ultrathin Film on Fe/Cu(001)

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