Mössbauer study of swift heavy ion irradiated Fe-Ni-Cr multilayers

S. Stichleutner, K. Havancsák, E. Kuzmann, G. Principi, C. Tosello

Sample preparation and irradiation

• FeNiCr multilayers were deposited by e-gun onto a plastic (UPILEX-S) substrate, at a pressure of about 6∙10-6 Pa.

• Irradiation was carried out with 246 MeV energy 86Kr8+ ions at room temperature and at a vacuum of about 10-3 Pa. The ion fluences attained were 1∙1014 ion∙cm-2 and 3∙1014 ion∙cm-2.

• Heat treatment of the irradiated samples was performed in a quartz tube in a furnace at temperatures of 450 ºC and 600 ºC isothermally for 3 h each time in a vacuum of about 10-3 Pa.

Mössbauer spectroscopy

excited state

ground state

coun

ts

velocity

γ-raydetector

Schematic representation of Mössbauer spectroscopy

I5/2

3/2

1/2

9 % 91 %

136 keV

14.4 keV

0

57Co

57Fe

γ-ray

Nuclear decay scheme of 57Co• Mössbauer spectroscopy is based

on the recoil-free resonance absorption of -photons observed with certain atomic nuclei.

Mössbauer spectroscopy

• Conversion electron Mössbauer spectra were recorded by a conventional mössbauer spectrometer (WISSEL) at room temperature with a flowing gas (96%He, 4%CH4) proportional counter and a 57Co(Rh) source of 1.85 GBq activity.

source

sample

detector

γ-rays

conversion electrons

Schematic representation of conversion electron

Mössbauer spectroscopy

shield

Effect of irradiation

• α-Fe

• ferromagneticFe-Ni-Cr solid solution

• paramagneticFe-Ni-Cr solid solution

-10 -8 -6 -4 -2 0 2 4 6 8 10

v (mm/s)

31014 ioncm-2

Cou

nts

11014 ioncm-2

as-deposited

Effect of irradiation

0 1x1014 2x1014 3x10140

20

40

60

80

100

Rel

ativ

e am

ount

of

met

asta

ble

phas

es (%

)

Irradiation dose (ioncm-2)

• Relative amount of the new metastable phases increases with the irradiation fluence.

Effect of heat treatment

• α-Fe

• ferromagneticFe-Ni-Cr solid solution

• paramagneticFe-Ni-Cr solid solution

• equilibriumFe-Ni-Cr alloy

-10 -8 -6 -4 -2 0 2 4 6 8 10

v (mm/s)

Cou

nts

600 ºC

450 ºC

31014 ioncm-2

Effect of heat treatment

0 200 400 600 8000

20

40

60

80

100

Rel

ativ

e am

ount

of e

quili

briu

mpa

ram

agne

tic p

hase

(%)

Temperature of annealing (oC)

• Relative amount of the equilibrium paramagnetic phase increases with the temperature of annealing.

Summary

• Energetic heavy ion irradiation proved to be an excellent tool to prepare Fe-Ni-Cr alloys by ion beam mixing.

• Irradiation of Fe-Ni-Cr multilayers by 246 MeV energy 86Kr8+ ions results metastable highly disordered ferromagnetic and paramagnetic phases which never occur in thermally prepared equilibrium alloys.

• Quantity of metastable phases increases with the dose of irradiation.

• Metastable phases of irradiated multilayers transform to the paramagnetic equilibrium phase due to heat treatment.

• Mössbauer spectroscopy is a sensitive analytical method to study the metastable and stable phases in Fe-Ni-Cr alloys.

Publications

• E. Kuzmann, G. Principi, C. Tosello, K. Havancsák, S. Stichleutner, I. Gerőcs, Z. Homonnay and A. Vértes, Mössbauer study of metastable phase formation in vacuum deposited FeNiCr multilayers due to swift heavy ion irradiation, Nucl. Instr. and Meth. B 183 (2001) 425-431

• E. Kuzmann, S. Stichleutner, M. El-Sharif, C. U. Chisholm, L. Sziráki and A. Vértes, Mössbauer investigation of electrodeposited Sn-Zn, Sn-Cr, Sn-Cr-Zn and Fe-Ni-Cr coatings, Hyp. Int. 141/142 (2002) 425-433

• E. Kuzmann, S. Stichleutner, M. El-Sharif, C. U. Chisholm, G. Principi, C. Tosello, K. Havancsák, I. Gerőcs and A. Vértes, Mössbauer studies of radiation effects in swift heavy ion irradiated Fe-Ni-Cr multilayers and electrodeposited alloys, Hyp. Int. C, 5 (2002) 591-594