摘要:

We set out to compare the ferromagnetic behavior of FexNi(1−x)and CoxNi(1−x)films of varying stoichiometry epitaxially grown on Cu(100). The thickness chosen was 5 ML over a wide alloy composition range. Using a scaling law for the thickness vs Curie temperature, we extrapolate the bulk fcc film thickness and plot the bulk fcc Curie temperature as a function of composition. The results suggest (a) that the Invar effect is quenched in these ultrathin pseudomorphic fcc films of FexNi(1−x)alloys and (b) the magnetic phase of Fe atoms is the low‐spin ferromagnetic phase. The CoxNi(1−x)films show the expected monotonic decrease inTcwith increasing Ni content.

ISSN:0734-211X    

DOI:10.1116/1.588805

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

The structure and composition of Fe films grown on As‐terminated GaAs(001)‐2×4 surfaces at 175 °C has been studiedinsituwith scanning tunneling microscopy (STM), photoelectron diffraction (PED), and x‐ray photoelectron spectroscopy (XPS). The GaAs surfaces were prepared by molecular beam epitaxy (MBE) and exhibited large atomically well‐ordered terraces. We find that the 2×4 reconstruction has a significant impact on the Fe nucleation and growth, with initial nucleation occurring at As‐dimer sites. STM reveals that the first half‐monolayer of Fe forms small two‐dimensional islands along the As‐dimer rows before growing onto the adjacent Ga‐rich rows, with no evidence of substrate disruption. PED indicates that the growth is predominantly layer by layer, with the growth front for thenth deposited layer limited to the (n+1)th layer. XPS spectra show that the Fe films include a concentration gradient of Ga and As out‐diffused from the interface, with some of the As segregating to the Fe surface, similar to previous results obtained for growth on non‐MBE prepared GaAs surfaces. Possible mechanisms for the film growth and the origins of the intermixing are discussed.

ISSN:0734-211X    

DOI:10.1116/1.588806

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

The Mn 3smultiplet splitting for a series of Mn overlayers on Ru(001) has been measured with synchrotron radiation photoemission spectroscopy. These overlayers were prepared by vapor deposition of Mn onto a Ru(001) substrate at a monolayer/minute dosing rate at room temperature. Under these conditions, the Mn overlayers grow pseudomorphically to multilayer coverages. It is found that this system exhibits a noticeable increase in the Mn 3smultiplet splitting and a positive binding energy shift as the coverage increases from monolayer to multilayer (12 ML). These results are attributed to the increase in the atomic volume, and hence the local magnetic moment at the Mn site on the average, with increasing coverage.

ISSN:0734-211X    

DOI:10.1116/1.588807

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

The temperature dependence of the uniaxial surface anisotropy,Ku(T), in ultrathin Fe films (4–10 atomic layers) grown on Cu(100) is determined by comparing the dipole and anisotropy energies at the spin reorientation temperature for films of varying thickness. It is observed that the uniaxial anisotropy has a weak temperature dependence compared to the bulk constants for Fe. The measured exponent of Γu=2.6(0.5) agrees well with thel(l+1)/2 law, which is obtained from a spin fluctuation model wherel=2 at the surface. This shows that the spin reorientation transition can be understood as being driven by thermal spin fluctuations.

ISSN:0734-211X    

DOI:10.1116/1.588808

出版商:American Vacuum Society    

年代:1996

数据来源: AIP

摘要:

Polarization‐dependent extended x‐ray absorption fine structure (PD‐EXAFS) measurements have been made on a single‐crystal 1000‐Å‐thick Co film deposited on (100) diamond. By comparing the EXAFS signals corresponding to the in‐plane and out‐of‐plane structure relative to the film plane, we clearly determine that the film does establish the face centered cubic (fcc) phase. Distinguishing between the hcp and fcc phases can thus be performed by qualitatively noting the polarization dependence of the Fourier transform peak amplitudes corresponding to the third and fourth coordination shells. This EXAFS study shows that the Co film studied here is unambiguously in the fcc phase. The Fourier transform peaks corresponding to the first nearest neighbors, parallel and perpendicular to the film, have been compared. Results indicate less than a 0.0075 Å difference between in‐plane and out‐of‐plane bondlengths, no significant change in coordination number and less than a 0.001 Å2difference in EXAFS Debye–Waller factors. All of these results indicate no tetragonal distortion of the fcc Co crystal lattice. This technique should prove valuable in future studies when trying to determine the crystallinity of thin films.

ISSN:0734-211X    

DOI:10.1116/1.588809

出版商:American Vacuum Society    

年代:1996

数据来源: AIP