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Ion implantation induced effects in surface properties of Fe85B15 metallic glass
Journal of Magnetism and Magnetic Materials 112 (1992) 367-368 North-Holland
1
Ion implantation induced effects in surface properties of metallic glass
Fe85B1e
Cs.S. D a r 6 c z i a, G. S e r f 6 z 6 a and P. Kollfir b a Central Research Institute for Physics, Hung. Acad. Sci., Budapest, Hungary b Faculty of Sci., P.J. Safdrik Unit'., Kogice, Czechoslocakia
Effects of implanted 100 keV energetic ions N ÷ and Ar + were investigated in FessB15 metallic glass using surface sensitive methods. Depending on the dosage ( < 4 x 1017 ions/cm 2) in the implanted layer (40-110 nm) partial crystallization, increased magnetization and perpendicular magnetic anisotropy were found.
1. Introduction During the last decade an increasing number of scientific work has been devoted to magnetic metallic glasses containing some crystalline precipitates. In the case of iron-based alloys significant improvement on high frequency soft magnetic behavior has been reached with about 13.01 volume fraction c~-Fe crystallites [1]. The usual method of getting this crystallites is a suitable annealing. On the other hand, the crystallization mostly starts at the irregularities of the surface. Even a crystallized surface itself can cause a perpendicular easy direction (through magnetostriction) and consequently preferred domain rotation against wall motion [2]. Irradiation techniques (laser annealing, ion irradiation, etc.) have the advantage that the crystallization in a controllable manner can be restricted to a desired depth. Ion implantation and irradiation at the same time have annealing and disordering effects. 2. Experimental FessB15 metallic glass ribbons were implanted on the shiny side with 1013 keV N + and Ar + ions up to dosage 4 × 1017 ions/cm 2 at temperature 80~C. The samples were investigated in air at Correspondence to: Dr. Cs.S. Dar6czi, I, FKI, P.O. Box 49, H-1525 Budapest 114, Hungary. Tel.: +36-1-1699-499; telefax: + 36-1-1550-694.
room temperature with X-ray diffraction, CEMS, FMR, STM and with a magneto-optical hysteresis-graph which utilizes the transversal Kerr-effect. In a previous work [3] we have investigated the influence of N ÷ implantation on F e - C r - S i - B metallic glasses. 3. Results Above dosages = 4 × 1016 N + / c m 2 and = 7 x 1016 A r + / c m 2 oL-Fe like crystalline phase appeared in the implanted regions 110 and 40 nm thick respectively, according to X-ray and CEMS measurements. For example at 1017 N + / c m 2 we found the majority of Fe atoms (59%) in the et-Fe phase. There were no sign of any other crystalline phase like Fe3B, F%B, Fe16N 2, etc. From the same dose levels a rapid increase of the surface coercive force occurred (from as quenched 100 A / m to 1 k A / m , or more) ;and the parallel F M R resonance peak splitted. The new peak took place at a higher magnetic field despite the increased saturation magnetization. This fact and the surface hysteresis curve showed ~n easy magnetization perpendicular to the same surface. When we used only 10 ~6 A r + / c m 2 implantation after 4 × 10 j6 N + / c m 2 preimplantation, the surface coercive force increased dramatically (fi'om ---200 A / m to 1.6 kA/m). We found the STM images of metallic glass FessB15 quite different. Somewhere it was cloud-like but a few lxm away
0304-8853.,/92/$05.00 © 1992 - Elsevier Science Publishers B.V. All rights reserved
368
Cs.S. Dardczi et al. / Ion implantation of metallic glass
stony. Till now we could not see any systematic difference between the STM images of implanted and non-implanted samples (fig. 1).
and even this was ineffective in crystallizing the surface up to dose 7 × 10 i~ Ar+/cm 2. 5. Conclusions
4. Discussion
In a common heat treatment the first step of crystallization (after pre-crystallization) of F e X - B type metallic glasses is the formation eutectic c¢-(Fe, X) and tetragonal (Fe, X)3B [4]. When the separation of the transition metal goes ahead (Fe, X)2B, (Fe, X)B, and ot-Fe phases arises from the metastable (Fe, X)3B. In respect to ion implantation it is important that amorphous (Fe,X)75B25 fairly resistant against crystallization [5] and inversely, (Fe, X)3B is very easy to be amorphised by irradiation. So we assume that the implantation blocked the way of crystallization via tetragonal Fe3B, because it was continuously amorphised. The difference of the two critical doses can be attributed to the chemical effect. Namely, during N ÷ implantation formation of (amorphous?) BN-rich regions may increase the Fe co~acentration in the residue. It should be stressed that the concentration of implanted ions and the deposited energy is almost 3 times larger in the case of Ar + ions in the implanted layer,
Ion implantation gives an opportunity to cause partial crystallization of a limited thick surface layer of F e - B metallic glasses, to get higher surface saturation magnetization ard to get perpendicular anisotropy. Ackno~/ledgement The authors are obliged to The National Organizing Committee of the SMM 10 carrying the outla~: ot their participation. References [1] D. Nathasingh, in: Power Conversion 7 (San Diego, 1980) Paper B2. [2] G. lqerzer and H.R. Hilzinger, J. Ivlagn. Magn. Mater. 62 (1986) 143. [3] G. Serfbz6, L.F. Kiss, Cs.S. Dar6czi, I~. Kisdi-Kosz6 and G. V~rtesy, IEEE Trans. Magn. 26 (1990) 1418. [4] L. Battezati, C. Antonione and G. Riontino, J. Non-Cryst. Solids 89 (1987) 114. [5~ T. Kem~ny, I. Vince and B. Fogarassy, Phys. Rev. B 20 (1979) 401.
Fig, i STM images of as-quenched (A) and 100 keV, 1017 N+/cm 2 implanted (B) FessBt5 samples. The scan area is 2 × 2 la,m 2, the height of while peaks is approximately 250 A.
1
Ion implantation induced effects in surface properties of metallic glass
Fe85B1e
Cs.S. D a r 6 c z i a, G. S e r f 6 z 6 a and P. Kollfir b a Central Research Institute for Physics, Hung. Acad. Sci., Budapest, Hungary b Faculty of Sci., P.J. Safdrik Unit'., Kogice, Czechoslocakia
Effects of implanted 100 keV energetic ions N ÷ and Ar + were investigated in FessB15 metallic glass using surface sensitive methods. Depending on the dosage ( < 4 x 1017 ions/cm 2) in the implanted layer (40-110 nm) partial crystallization, increased magnetization and perpendicular magnetic anisotropy were found.
1. Introduction During the last decade an increasing number of scientific work has been devoted to magnetic metallic glasses containing some crystalline precipitates. In the case of iron-based alloys significant improvement on high frequency soft magnetic behavior has been reached with about 13.01 volume fraction c~-Fe crystallites [1]. The usual method of getting this crystallites is a suitable annealing. On the other hand, the crystallization mostly starts at the irregularities of the surface. Even a crystallized surface itself can cause a perpendicular easy direction (through magnetostriction) and consequently preferred domain rotation against wall motion [2]. Irradiation techniques (laser annealing, ion irradiation, etc.) have the advantage that the crystallization in a controllable manner can be restricted to a desired depth. Ion implantation and irradiation at the same time have annealing and disordering effects. 2. Experimental FessB15 metallic glass ribbons were implanted on the shiny side with 1013 keV N + and Ar + ions up to dosage 4 × 1017 ions/cm 2 at temperature 80~C. The samples were investigated in air at Correspondence to: Dr. Cs.S. Dar6czi, I, FKI, P.O. Box 49, H-1525 Budapest 114, Hungary. Tel.: +36-1-1699-499; telefax: + 36-1-1550-694.
room temperature with X-ray diffraction, CEMS, FMR, STM and with a magneto-optical hysteresis-graph which utilizes the transversal Kerr-effect. In a previous work [3] we have investigated the influence of N ÷ implantation on F e - C r - S i - B metallic glasses. 3. Results Above dosages = 4 × 1016 N + / c m 2 and = 7 x 1016 A r + / c m 2 oL-Fe like crystalline phase appeared in the implanted regions 110 and 40 nm thick respectively, according to X-ray and CEMS measurements. For example at 1017 N + / c m 2 we found the majority of Fe atoms (59%) in the et-Fe phase. There were no sign of any other crystalline phase like Fe3B, F%B, Fe16N 2, etc. From the same dose levels a rapid increase of the surface coercive force occurred (from as quenched 100 A / m to 1 k A / m , or more) ;and the parallel F M R resonance peak splitted. The new peak took place at a higher magnetic field despite the increased saturation magnetization. This fact and the surface hysteresis curve showed ~n easy magnetization perpendicular to the same surface. When we used only 10 ~6 A r + / c m 2 implantation after 4 × 10 j6 N + / c m 2 preimplantation, the surface coercive force increased dramatically (fi'om ---200 A / m to 1.6 kA/m). We found the STM images of metallic glass FessB15 quite different. Somewhere it was cloud-like but a few lxm away
0304-8853.,/92/$05.00 © 1992 - Elsevier Science Publishers B.V. All rights reserved
368
Cs.S. Dardczi et al. / Ion implantation of metallic glass
stony. Till now we could not see any systematic difference between the STM images of implanted and non-implanted samples (fig. 1).
and even this was ineffective in crystallizing the surface up to dose 7 × 10 i~ Ar+/cm 2. 5. Conclusions
4. Discussion
In a common heat treatment the first step of crystallization (after pre-crystallization) of F e X - B type metallic glasses is the formation eutectic c¢-(Fe, X) and tetragonal (Fe, X)3B [4]. When the separation of the transition metal goes ahead (Fe, X)2B, (Fe, X)B, and ot-Fe phases arises from the metastable (Fe, X)3B. In respect to ion implantation it is important that amorphous (Fe,X)75B25 fairly resistant against crystallization [5] and inversely, (Fe, X)3B is very easy to be amorphised by irradiation. So we assume that the implantation blocked the way of crystallization via tetragonal Fe3B, because it was continuously amorphised. The difference of the two critical doses can be attributed to the chemical effect. Namely, during N ÷ implantation formation of (amorphous?) BN-rich regions may increase the Fe co~acentration in the residue. It should be stressed that the concentration of implanted ions and the deposited energy is almost 3 times larger in the case of Ar + ions in the implanted layer,
Ion implantation gives an opportunity to cause partial crystallization of a limited thick surface layer of F e - B metallic glasses, to get higher surface saturation magnetization ard to get perpendicular anisotropy. Ackno~/ledgement The authors are obliged to The National Organizing Committee of the SMM 10 carrying the outla~: ot their participation. References [1] D. Nathasingh, in: Power Conversion 7 (San Diego, 1980) Paper B2. [2] G. lqerzer and H.R. Hilzinger, J. Ivlagn. Magn. Mater. 62 (1986) 143. [3] G. Serfbz6, L.F. Kiss, Cs.S. Dar6czi, I~. Kisdi-Kosz6 and G. V~rtesy, IEEE Trans. Magn. 26 (1990) 1418. [4] L. Battezati, C. Antonione and G. Riontino, J. Non-Cryst. Solids 89 (1987) 114. [5~ T. Kem~ny, I. Vince and B. Fogarassy, Phys. Rev. B 20 (1979) 401.
Fig, i STM images of as-quenched (A) and 100 keV, 1017 N+/cm 2 implanted (B) FessBt5 samples. The scan area is 2 × 2 la,m 2, the height of while peaks is approximately 250 A.