Modification of local order in FePd films by low energy He{sup +} irradiation

Journal Article · Tue Jul 01 00:00:00 EDT 2008 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.2938027· OSTI ID:21137384

Merkel, D G; Tancziko, F; Sajti, Sz; Major, M; Nemeth, A; Bottyan, L ^[1]; Horvath, Z E; Waizinger, J ^[2]; Stankov, S ^[3]; Kovacs, A ^[4]

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1. KFKI Research Institute for Particle and Nuclear Physics, P.O. Box 49, H 1525 Budapest (Hungary)
2. Research Institute for Technical Physics and Materials Science, P.O. Box 49, H 1525 Budapest (Hungary)
3. European Synchrotron Radiation Facility, BP 220, 38043 Grenoble Cedex 9 (France)
4. The Institute of Scientific and Industrial Research, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047 (Japan)

Owing to their strong perpendicular magnetic anisotropy, FePd, CoPd, and their Co(Fe)Pt counterparts are candidate materials for ultrahigh density magnetic recording. The stability and magnetic properties of such films are largely dependent on the orientation and local distribution of the L1{sub 0} FePd phase fraction. Therefore, the formation and transformation of the L1{sub 0} phase in such thin films have been the subject of continued interest. Highly ordered epitaxial FePd(001) thin films (with an L1{sub 0} phase fraction of 0.81) were prepared by molecular-beam epitaxy on a MgO(001) substrate. The effect of postgrown room temperature, 130 keV He{sup +} irradiation was investigated at fluences up to 14.9x10{sup 15} ions/cm{sup 2}. X-ray diffraction and conversion electron Moessbauer spectroscopy revealed that with increasing fluence, the L1{sub 0} FePd phase decomposes into the face centered cubic phase with random Fe and Pd occupation of the sites. A partially ordered local environment exhibiting a large hyperfine magnetic field also develops. Upon He{sup +} irradiation, the lattice parameter c of the FePd L1{sub 0} structure increases and the long range order parameter S steeply decreases. The Fe-Fe nearest-neighbor coordination in the Fe-containing environments increases on average from Fe{sub 47}Pd{sub 53} to Fe{sub 54}Pd{sub 46}, indicating a tendency of formation iron-rich clusters. The equilibrium parameters corresponding to the equiatomic L1{sub 0} phase were found at different fluences by conversion electron Moessbauer spectroscopy and by x-ray diffraction a difference, from which a plane-perpendicular compressive stress and a corresponding in-plane tensile stress are conjectured. The steep increase in the interface roughness above 7.4x10{sup 15} ions/cm{sup 2} is interpreted as a percolation-type behavior related to the high diffusion anisotropy in the L1{sub 0} phase.

• OSTI ID: 21137384
• Journal Information: Journal of Applied Physics, Journal Name: Journal of Applied Physics Journal Issue: 1 Vol. 104; ISSN JAPIAU; ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ANISOTROPY
COBALT ALLOYS
CRYSTAL GROWTH
ELECTRON SPECTRA
FCC LATTICES
HELIUM IONS
ION BEAMS
IRON ALLOYS
KEV RANGE 100-1000
LATTICE PARAMETERS
MAGNESIUM OXIDES
MAGNETIC PROPERTIES
MOESSBAUER EFFECT
MOLECULAR BEAM EPITAXY
ORDER PARAMETERS
PALLADIUM ALLOYS
PHASE TRANSFORMATIONS
TEMPERATURE RANGE 0273-0400 K
THIN FILMS
X-RAY DIFFRACTION