Ferrimagnetic ordering of single crystal Fe1−xGax thin films

Journal of Applied Physics

Arenholz

2015

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The alloy composition and elemental magnetic moments of bcc single crystal films of compositionally graded FexMn1−x films (20 nm thick films with 0.8 ≤ x ≤ 0.9) grown on MgO(001) are spatially mapped using X-ray absorption spectroscopy and magnetic circular dichroism. Electron diffraction measurements on single composition samples confirmed that the structure of FexMn1−x films remained epitaxial and in the bcc phase from 0.65 ≤ x ≤ 1, but rotated 45° with respect to the MgO(001) surface net. This is beyond the bulk bcc stability limit of x = 0.88. The Fe moment is found to gradually reduce with increasing Mn content with a very abrupt decline at x = 0.85, a slightly higher composition than observed in the bulk. Surprisingly, the Mn exhibits a very small net moment (<0.1 μB) at all compositions, suggesting a complex Mn spin structure.

Section: Methodssupporting

confidence: 60%

Moment mapping of body-centered-cubic FexMn1−x alloy films on MgO(001)

Idzerda

Journal of Applied Physics

Arenholz

2015

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“…For all growths, the Fe source was always maintained at constant temperature of ~1400 °C (1673 K) assuring a constant rate of Fe deposition while the Mn source was held at various temperatures to achieve different Mn flux rates and therefore different alloy stoichiometries for the films. The films were deposited with the substrate held at 150-160 °C (423-433 K) to ensure good quality, ~20nm thick films [24]. Deposition fluxes were monitored by quadrupole mass spectrometry (QMS).…”

Section: Methodsmentioning

confidence: 99%

Elemental moment variation of bcc FexMn1−x on MgO(001)

Journal of Magnetism and Magnetic Materials

Snow

Arenholz

et al. 2017

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We report the growth, structural characterization, and electronic structure evolution of epitaxially grown bcc FexMn1-x on MgO(001). It is observed that the 20 nm thick FexMn1-x alloy films remained bcc from 0.65 ≤ x ≤ 1, much beyond the bulk stability range of 0.88 ≤ x ≤ 1. X-ray absorption spectroscopy and Xray magnetic circular dichroism show that both the Fe and Mn L3 binding energies slightly increase with Mn incorporation and that the elemental moment of Fe in the 20 nm crystalline bcc alloy film remain nearly constant, then shows a dramatic collapse near x~0.84. The Mn MCD intensity is found to be small at all compositions that exhibit ferromagnetism

“…The 2 nm Fe buffer layer was 5 deposited with the Fe knudsen cell also held at 1320°C which resulted in a deposition rate of about 0.1 nm/minute. An ideal substrate temperature for growth of Fe on MgO was found to be around 160°C [20], and this was used for both the Fe buffer layer and the Co 1-x Mn x growths. The substrate temperature was then reduced to below 100°C for the Al cap layer.…”

Section: Growthmentioning

confidence: 99%

Enhanced moments in bcc Co1−Mn on MgO(001)

Snow

Journal of Magnetism and Magnetic Materials

N’Diaye

et al. 2016

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A 40% enhancement of the Co magnetic moment has been found for thin films of bcc Co 1-x Mn x grown by molecular beam epitaxy on a 2 nm bcc Fe buffer layer on MgO(001). Although the bcc phase cannot be stabilized in the bulk, we confirm that it is stable as an epitaxial film in the composition range x = 0-0.7. Using X-ray absorption spectroscopy and X-ray magnetic circular dichroism, we show that the Co moment is a maximum of 2.38 µ B at x = 0.24, while the net Mn moment remains roughly constant until x = 0.24, then drops steadily. Mn is found to align parallel with Co for all ferromagnetic concentrations, up to x = 0.7, where the total moment of the film abruptly collapses to zero, most likely due to the onset of the observed structural instability.