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Annealing and neutron-irradiation effects on the permeability of Fe86Zr7B6Cu1
Physica B 327 (2003) 311–314
Annealing and neutron-irradiation effects on the permeability of Fe86Zr7B6Cu1 Y.S. Kima, M.H. Phana, S.C. Yua, K.S. Kima,*, H.B. Leeb, B.G. Kimc, Y.H. Kangc b
a Department of Physics, Chungbuk National University, Cheongju 361-763, South Korea Department of Physics Education, Kongju National University, Kongju 314-701, South Korea c HANARO Center, Korea Atomic Energy Research Institute, Taejon 305-600, South Korea
Abstract The effects of annealing and neutron irradiation on the magnetic properties of amorphous Fe86Zr7B6Cu1 alloys have been investigated by means of the changes of the longitudinal permeability ratio (LPR). In general, there are no differences in magnitude and shape of the LPR curves between as-quenched amorphous and neutron-irradiated samples. This indicates that the effects of neutron irradiation on the magnetic properties of the as-quenched sample are negligible. But a drastic decrease, caused by neutron irradiation, is observed in the magnitude of the LPR and the broadening of the LPR curves of the sample annealed at 6501C, which has a maximum value of the LPR due to the presence of ultra-soft magnetic materials. This can be attributed to a decrease in domain wall displacement and to a magnetization rotation due to the neutron irradiation effect. The local anisotropy plays a significant role in the case of this sample. r 2002 Elsevier Science B.V. All rights reserved. PACS: 75.50.Kj; 75.60.Ch; 75.75.+a Keywords: Annealing; Neutron irradiation; Anisotropy; Amorphous alloys
1. Introduction In the past years, the giant magneto-impedance (GMI) effect in amorphous soft ferromagnetic alloys has attracted much attention due to their potential for magnetic sensors applications [1–3]. The GMI effect can be only obtained in ultra-soft magnetic materials with a nearly zero magnetostriction constant, a nearly zero coercivity, and a *Corresponding author. Tel. :+82-43-261-2269; fax: +8243-275-6416. E-mail address: [email protected] (K.S. Kim).
high circumferential permeability [2–4]. Therefore, efforts are required to look for proper treatments that can improve the ultra-soft magnetic properties of these materials [2,4]. Recently, the influence of neutron irradiation on the magnetic properties of amorphous alloys has been studied. The observed changes in various magnetic parameters such as Curie temperature [5], magnetic permeability [6] and hysteresis loop parameters [7] clearly demonstrate that amorphous alloys can be structurally modified by neutron irradiation. Notably, studies of the frequency spectra of the susceptibility in the as-quenched amorphous and
0921-4526/03/$ - see front matter r 2002 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 1 - 4 5 2 6 ( 0 2 ) 0 1 7 7 6 - 3
Y.S. Kim et al. / Physica B 327 (2003) 311–314
neutron-irradiated ribbons have been frequently considered [8–9]. On the other hand, studies of the GMI effect have shown that changes of the magneto-impedance, such as the GMI effect, are closely related to those of the longitudinal permeability ratio (LPR) [2,10]. Therefore, the evaluation of soft-magnetic parameters as well as magnetization processes in amorphous alloys can be made by studying the changes of the LPR. In the present work, the annealing and neutronirradiation effects on the magnetic properties of amorphous Fe86Zr7B6Cu1 alloys are studied by means of LPR measurements.
10 Fe86Zr7B6Cu1 8 6 4 2 0 -150
2. Experimental Fe86Zr7B6Cu1 ribbons of 4 mm width and 20 mm thickness were prepared by the rapid quenching technique in vacuum. The amorphous state of the samples was confirmed by X-ray diffractometry. The samples were studied under the following procedures: neutron irradiated (No. 1), annealing at 6501C in a vacuum (No. 2), neutron irradiated after annealing at 6501C (No. 3). The samples (No. 1 and 3) were irradiated for 72 h using the HANARO research reactor at the Korea Atomic Energy Research Institute. The fluxes of thermal (nth ) and fast (nf ) neutrons were 3.09 1013 and 1.87 1011nth cm2 s1, respectively. The total integrated fast neutron fluences were 19.2 1014, 2.63 1015 and 4.85 1016nf cm2. We have designed a measurement system for the incremental permeability. A detailed description can be found elsewhere [2].
3. Results and discussion The permeability ratio (PR) is defined as Dm=mðHmax Þ ¼ 1 mðHÞ=mðHmax Þ : Therefore, the LPR is defined as the PR measured along the external field. The LPR has been measured as a function of external magnetic field at various frequencies from 1 MHz up to 5 MHz for all the samples. As shown in Fig. 1, the LPR curves of the as-quenched sample all exhibit a peak at H ¼ 0: With increasing frequency, the magnitude of the
f = 1 MHz f = 2 MHz f = 3 MHz f = 4 MHz f = 5 MHz
as-quenched sample
LPR (%)
312
-100
-50
0
50
100
150
H (Oe) Fig. 1. LPR curves as a function of magnetic field measured at various frequencies for the as-quenched sample.
LPR monotonically decreases while the shape of the LPR curves becomes broader. A similar tendency is observed for the remaining samples. Since the external magnetic field is a hard axis field with respect to the circumferential anisotropy, the magnetic field applied along the ribbon axis will suppress the circular magnetization by domain wall movements at low frequencies, or the motion of localized magnetic moments at high frequencies. As the external applied field increases, the circumferential permeability decreases rapidly. As a result, the peaks of the LPR curves are obtained around zero magnetic field. The broadening of the LPR curves as frequency increases could be attributed to the frequency dependence of the permeability [2]. In order to further interpret the broadening of the LPR curves, a model for the transverse biased permeability in thick ferromagnetic films can be adopted [11]. According to this model, it is the eddy current damping and the ripple field HR incorporating with the anisotropy HK that give rise to the peak of permeability at an external field as well as the broadening of LPR curves at high frequencies. From Fig. 2 we can see that there are in most cases no differences both in magnitude and shape of the LPR curves between as-quenched amorphous and neutron-irradiated samples. This indicates a negligible effect of the
Y.S. Kim et al. / Physica B 327 (2003) 311–314
(No. 1)
LPR (%)
8 6
f = 1 MHz f = 2 MHz f = 3 MHz f = 4 MHz f = 5 MHz
15 Fe86Zr7B6Cu1 (No. 3)
12 LPR (%)
f = 1 MHz f = 2 MHz f = 3 MHz f = 4 MHz f = 5 MHz
10 Fe86Zr7B6Cu1
313
9 6
4 3
2 0
0
-150
-150
-100
-50
0
50
100
Fig. 2. LPR curves as a function of magnetic field measured at various frequencies for the neutron irradiated sample (No. 1).
30
10 5
100
150
35 Fe86Zr7B6Cu1
30
as-quenched No. 1 No. 2 No. 3
25
20 15
50
Fig. 4. LPR curves as a function of magnetic field measured at various frequencies for the neutron irradiated sample after annealing at 6501C (No. 3).
LPRmax(%)
LPR (%)
25
0 H (Oe)
f = 1 MHz f = 2 MHz f = 3 MHz f = 4 MHz f = 5 MHz
Fe86Zr7B6Cu1 (No. 2)
-50
150
H (Oe)
35
-100
20 15 10
0 -5 -150
5 -100
-50
0
50
100
150
H (Oe) Fig. 3. LPR curves as a function of magnetic field measured at various frequencies for the 6501C-annealed sample (No. 2).
neutron irradiation on the magnetic properties of the as-quenched sample. But the alloy annealed at 6501C (No. 2) has a maximum value of the incremental permeability ratio as well as an improvement in the shape of the LPR curves, arising from the ultra-soft magnetic properties due to the heat treatment (see Fig. 3). It is noteworthy that the magnitudes of the LPR of No. 3, shown in Fig. 4, with increasing frequency are larger than those shown in Figs. 1 and 2, but are drastically
0
1
2
3
4
5
Frequency ( MHz) Fig. 5. Frequency dependence of the maximum LPR for all investigated samples.
reduced compared with No. 2 in Fig. 3. Additionally, the largest broadening occurs in the LPR curves of No. 3. This can be attributed to a reduction in domain wall displacement and to a magnetization rotation due to the neutron irradiation effect [2,8]. Apart from that, the asymmetric behavior appearing in the LPR peaks of No. 3 might arise from the role played by local anisotropy at low fields [2–4,10]. The frequency dependence of the maximum LPR for all the
314
Y.S. Kim et al. / Physica B 327 (2003) 311–314
samples is shown in Fig. 5. Obviously, only the magnetic properties of the nanocrystalline alloy (No. 2) are changed by neutron irradiation, but not for the as-quenched amorphous alloy. In other words, the local anisotropy caused by neutron irradiation plays a significant role in the case of No. 3.
Acknowledgements The authors would like to thank to Prof. V. Srinivas for helpful discussions and correction of the English. Research at Chungbuk National University was supported by the Korea Research Foundation Grant (KRF-2001-005-D20010).
References 4. Conclusions The annealing and neutron-irradiation effects on the magnetic properties of amorphous Fe86Zr7B6Cu1 alloys have been investigated by LPR measurements. The sample annealed at 6501C has a maximum value of the LPR due to the presence of ultra-soft magnetic materials. The magnetic properties of this sample are drastically reduced under neutron irradiation. It can be attributed to the reduction in domain wall displacement and to magnetization rotation by the neutron-irradiation effect. The local anisotropy also plays a significant role in this sample. A negligible effect of neutron irradiation on the as-quenched amorphous sample is observed.
[1] L.V. Panina, K. Mohri, J. Magn. Soc. Jpn. 19 (1995) 265. [2] H.B. Lee, Y.K. Kim, T.K. Kim, Y.H. Song, S.C. Yu, J. Appl. Phys. 85 (1999) 5429. [3] K. Mandal, S.P. Mandal, S. Puerta, M. V!azquez, A. Hernando, J. Alloys Compd. 326 (2001) 201. [4] F. Amalou, M.A.M. Gijs, J. Appl. Phys. 90 (2002) 3466. [5] P.J. Grundy, G.A. Jones, S.F.H. Parker, IEEE Trans. Magn. 19 (1983) 1913. [6] R.D. Brown, J.R. Cost, J.T. Stanley, J. Appl. Phys. 55 (1984) 1754. [7] M. Miglierini, I. Skorvanek, Mater. Sci. Eng. A147 (1991) 101. [8] H.C. Kim, S.C. Yu, C.G. Kim, H.S. Han, W.K. Cho, J. Magn. Magn. Mater. 215–216 (2000) 355. [9] H.C. Kim, S.C. Yu, C.G. Kim, H.S. Han, W.K. Cho, Mater. Sci. Eng. A304–306 (2001) 1030. [10] H.B. Lee, K.J. Lee, Y.K. Kim, T.K. Kim, K.S. Kim, S.C. Yu, J. Alloys Compd. 326 (2001) 313. [11] W.D. Doyle, X. He, P. Tang, T. Jangielinski, N. Smith, J. Appl. Phys. 73 (1993) 5995.
Annealing and neutron-irradiation effects on the permeability of Fe86Zr7B6Cu1 Y.S. Kima, M.H. Phana, S.C. Yua, K.S. Kima,*, H.B. Leeb, B.G. Kimc, Y.H. Kangc b
a Department of Physics, Chungbuk National University, Cheongju 361-763, South Korea Department of Physics Education, Kongju National University, Kongju 314-701, South Korea c HANARO Center, Korea Atomic Energy Research Institute, Taejon 305-600, South Korea
Abstract The effects of annealing and neutron irradiation on the magnetic properties of amorphous Fe86Zr7B6Cu1 alloys have been investigated by means of the changes of the longitudinal permeability ratio (LPR). In general, there are no differences in magnitude and shape of the LPR curves between as-quenched amorphous and neutron-irradiated samples. This indicates that the effects of neutron irradiation on the magnetic properties of the as-quenched sample are negligible. But a drastic decrease, caused by neutron irradiation, is observed in the magnitude of the LPR and the broadening of the LPR curves of the sample annealed at 6501C, which has a maximum value of the LPR due to the presence of ultra-soft magnetic materials. This can be attributed to a decrease in domain wall displacement and to a magnetization rotation due to the neutron irradiation effect. The local anisotropy plays a significant role in the case of this sample. r 2002 Elsevier Science B.V. All rights reserved. PACS: 75.50.Kj; 75.60.Ch; 75.75.+a Keywords: Annealing; Neutron irradiation; Anisotropy; Amorphous alloys
1. Introduction In the past years, the giant magneto-impedance (GMI) effect in amorphous soft ferromagnetic alloys has attracted much attention due to their potential for magnetic sensors applications [1–3]. The GMI effect can be only obtained in ultra-soft magnetic materials with a nearly zero magnetostriction constant, a nearly zero coercivity, and a *Corresponding author. Tel. :+82-43-261-2269; fax: +8243-275-6416. E-mail address: [email protected] (K.S. Kim).
high circumferential permeability [2–4]. Therefore, efforts are required to look for proper treatments that can improve the ultra-soft magnetic properties of these materials [2,4]. Recently, the influence of neutron irradiation on the magnetic properties of amorphous alloys has been studied. The observed changes in various magnetic parameters such as Curie temperature [5], magnetic permeability [6] and hysteresis loop parameters [7] clearly demonstrate that amorphous alloys can be structurally modified by neutron irradiation. Notably, studies of the frequency spectra of the susceptibility in the as-quenched amorphous and
0921-4526/03/$ - see front matter r 2002 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 1 - 4 5 2 6 ( 0 2 ) 0 1 7 7 6 - 3
Y.S. Kim et al. / Physica B 327 (2003) 311–314
neutron-irradiated ribbons have been frequently considered [8–9]. On the other hand, studies of the GMI effect have shown that changes of the magneto-impedance, such as the GMI effect, are closely related to those of the longitudinal permeability ratio (LPR) [2,10]. Therefore, the evaluation of soft-magnetic parameters as well as magnetization processes in amorphous alloys can be made by studying the changes of the LPR. In the present work, the annealing and neutronirradiation effects on the magnetic properties of amorphous Fe86Zr7B6Cu1 alloys are studied by means of LPR measurements.
10 Fe86Zr7B6Cu1 8 6 4 2 0 -150
2. Experimental Fe86Zr7B6Cu1 ribbons of 4 mm width and 20 mm thickness were prepared by the rapid quenching technique in vacuum. The amorphous state of the samples was confirmed by X-ray diffractometry. The samples were studied under the following procedures: neutron irradiated (No. 1), annealing at 6501C in a vacuum (No. 2), neutron irradiated after annealing at 6501C (No. 3). The samples (No. 1 and 3) were irradiated for 72 h using the HANARO research reactor at the Korea Atomic Energy Research Institute. The fluxes of thermal (nth ) and fast (nf ) neutrons were 3.09 1013 and 1.87 1011nth cm2 s1, respectively. The total integrated fast neutron fluences were 19.2 1014, 2.63 1015 and 4.85 1016nf cm2. We have designed a measurement system for the incremental permeability. A detailed description can be found elsewhere [2].
3. Results and discussion The permeability ratio (PR) is defined as Dm=mðHmax Þ ¼ 1 mðHÞ=mðHmax Þ : Therefore, the LPR is defined as the PR measured along the external field. The LPR has been measured as a function of external magnetic field at various frequencies from 1 MHz up to 5 MHz for all the samples. As shown in Fig. 1, the LPR curves of the as-quenched sample all exhibit a peak at H ¼ 0: With increasing frequency, the magnitude of the
f = 1 MHz f = 2 MHz f = 3 MHz f = 4 MHz f = 5 MHz
as-quenched sample
LPR (%)
312
-100
-50
0
50
100
150
H (Oe) Fig. 1. LPR curves as a function of magnetic field measured at various frequencies for the as-quenched sample.
LPR monotonically decreases while the shape of the LPR curves becomes broader. A similar tendency is observed for the remaining samples. Since the external magnetic field is a hard axis field with respect to the circumferential anisotropy, the magnetic field applied along the ribbon axis will suppress the circular magnetization by domain wall movements at low frequencies, or the motion of localized magnetic moments at high frequencies. As the external applied field increases, the circumferential permeability decreases rapidly. As a result, the peaks of the LPR curves are obtained around zero magnetic field. The broadening of the LPR curves as frequency increases could be attributed to the frequency dependence of the permeability [2]. In order to further interpret the broadening of the LPR curves, a model for the transverse biased permeability in thick ferromagnetic films can be adopted [11]. According to this model, it is the eddy current damping and the ripple field HR incorporating with the anisotropy HK that give rise to the peak of permeability at an external field as well as the broadening of LPR curves at high frequencies. From Fig. 2 we can see that there are in most cases no differences both in magnitude and shape of the LPR curves between as-quenched amorphous and neutron-irradiated samples. This indicates a negligible effect of the
Y.S. Kim et al. / Physica B 327 (2003) 311–314
(No. 1)
LPR (%)
8 6
f = 1 MHz f = 2 MHz f = 3 MHz f = 4 MHz f = 5 MHz
15 Fe86Zr7B6Cu1 (No. 3)
12 LPR (%)
f = 1 MHz f = 2 MHz f = 3 MHz f = 4 MHz f = 5 MHz
10 Fe86Zr7B6Cu1
313
9 6
4 3
2 0
0
-150
-150
-100
-50
0
50
100
Fig. 2. LPR curves as a function of magnetic field measured at various frequencies for the neutron irradiated sample (No. 1).
30
10 5
100
150
35 Fe86Zr7B6Cu1
30
as-quenched No. 1 No. 2 No. 3
25
20 15
50
Fig. 4. LPR curves as a function of magnetic field measured at various frequencies for the neutron irradiated sample after annealing at 6501C (No. 3).
LPRmax(%)
LPR (%)
25
0 H (Oe)
f = 1 MHz f = 2 MHz f = 3 MHz f = 4 MHz f = 5 MHz
Fe86Zr7B6Cu1 (No. 2)
-50
150
H (Oe)
35
-100
20 15 10
0 -5 -150
5 -100
-50
0
50
100
150
H (Oe) Fig. 3. LPR curves as a function of magnetic field measured at various frequencies for the 6501C-annealed sample (No. 2).
neutron irradiation on the magnetic properties of the as-quenched sample. But the alloy annealed at 6501C (No. 2) has a maximum value of the incremental permeability ratio as well as an improvement in the shape of the LPR curves, arising from the ultra-soft magnetic properties due to the heat treatment (see Fig. 3). It is noteworthy that the magnitudes of the LPR of No. 3, shown in Fig. 4, with increasing frequency are larger than those shown in Figs. 1 and 2, but are drastically
0
1
2
3
4
5
Frequency ( MHz) Fig. 5. Frequency dependence of the maximum LPR for all investigated samples.
reduced compared with No. 2 in Fig. 3. Additionally, the largest broadening occurs in the LPR curves of No. 3. This can be attributed to a reduction in domain wall displacement and to a magnetization rotation due to the neutron irradiation effect [2,8]. Apart from that, the asymmetric behavior appearing in the LPR peaks of No. 3 might arise from the role played by local anisotropy at low fields [2–4,10]. The frequency dependence of the maximum LPR for all the
314
Y.S. Kim et al. / Physica B 327 (2003) 311–314
samples is shown in Fig. 5. Obviously, only the magnetic properties of the nanocrystalline alloy (No. 2) are changed by neutron irradiation, but not for the as-quenched amorphous alloy. In other words, the local anisotropy caused by neutron irradiation plays a significant role in the case of No. 3.
Acknowledgements The authors would like to thank to Prof. V. Srinivas for helpful discussions and correction of the English. Research at Chungbuk National University was supported by the Korea Research Foundation Grant (KRF-2001-005-D20010).
References 4. Conclusions The annealing and neutron-irradiation effects on the magnetic properties of amorphous Fe86Zr7B6Cu1 alloys have been investigated by LPR measurements. The sample annealed at 6501C has a maximum value of the LPR due to the presence of ultra-soft magnetic materials. The magnetic properties of this sample are drastically reduced under neutron irradiation. It can be attributed to the reduction in domain wall displacement and to magnetization rotation by the neutron-irradiation effect. The local anisotropy also plays a significant role in this sample. A negligible effect of neutron irradiation on the as-quenched amorphous sample is observed.
[1] L.V. Panina, K. Mohri, J. Magn. Soc. Jpn. 19 (1995) 265. [2] H.B. Lee, Y.K. Kim, T.K. Kim, Y.H. Song, S.C. Yu, J. Appl. Phys. 85 (1999) 5429. [3] K. Mandal, S.P. Mandal, S. Puerta, M. V!azquez, A. Hernando, J. Alloys Compd. 326 (2001) 201. [4] F. Amalou, M.A.M. Gijs, J. Appl. Phys. 90 (2002) 3466. [5] P.J. Grundy, G.A. Jones, S.F.H. Parker, IEEE Trans. Magn. 19 (1983) 1913. [6] R.D. Brown, J.R. Cost, J.T. Stanley, J. Appl. Phys. 55 (1984) 1754. [7] M. Miglierini, I. Skorvanek, Mater. Sci. Eng. A147 (1991) 101. [8] H.C. Kim, S.C. Yu, C.G. Kim, H.S. Han, W.K. Cho, J. Magn. Magn. Mater. 215–216 (2000) 355. [9] H.C. Kim, S.C. Yu, C.G. Kim, H.S. Han, W.K. Cho, Mater. Sci. Eng. A304–306 (2001) 1030. [10] H.B. Lee, K.J. Lee, Y.K. Kim, T.K. Kim, K.S. Kim, S.C. Yu, J. Alloys Compd. 326 (2001) 313. [11] W.D. Doyle, X. He, P. Tang, T. Jangielinski, N. Smith, J. Appl. Phys. 73 (1993) 5995.