- Email: [email protected]
A flexible way to modulate the detection range of anisotropic magnetoresistance by exchange bias field
Journal of Magnetism and Magnetic Materials 476 (2019) 469–471
Contents lists available at ScienceDirect
Journal of Magnetism and Magnetic Materials journal homepage: www.elsevier.com/locate/jmmm
Research articles
A flexible way to modulate the detection range of anisotropic magnetoresistance by exchange bias field
T
⁎
XiaoLi Tang , Wei Du, JinBiao Yu, HuaiWu Zhang, Hua Su State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, Sichuan 610054, China
A B S T R A C T
A series of Ta/FeMn/[NiFe/FeMn]n/Ta films was grown through DC-sputtering. They acted as a new structure of multilayer anisotropic magnetoresistance (AMR). Based on the exchange bias (EB) field producing at the NiFe/FeMn interface, the linear range and saturation field along the multilayer’s hard axis enlarged when compared with a single NiFe layer. The linear range and saturation field decided the detection range of the AMR. Therefore, by fixing the total thickness of magnetic NiFe layer and selecting different number of n in multilayer, each thickness of NiFe layer was changed to tune EB field. Then, the detection range was modulated by varying exchange bias fields. Adopting this method, the detection range could be easy to control and adjustable from 20.5 Gs to 116 Gs on the basis of AMR responses. The proposed method promotes the application of the AMR effect over a wide magnetic detection area.
1. Introduction The anisotropic magnetoresistance (AMR) effect, which originates from the anisotropic scattering of conduction electrons due to spin–orbit interactions, has been extensively studied over the past few decades. The application of AMR thin films as magnetic sensors and detectors has been proposed because their resistance varies under magnetic fields [1–3]. Although the magnetoresistance effects of newly discovered giant magnetoresistance and tunneling magnetoresistance are more intense than those of AMR, the AMR effect can be achieved with only one magnetic layer. Given this advantage, AMR structures are simple and easy to fabricate and integrate. Therefore, AMR sensors are in high demands for applications in information processing, automation, and navigation, as well as military fields [4–6]. NiFe permalloy is the best material for use in AMR devices because of its high AMR amplitude and sensitivity and low cost. In magnetic detection, linearity and reversibility require the coherent rotation of magnetization under the detection direction. The sensitive direction or detection field is always along the hard layer of the magnetic film to meet this requirement. Therefore, the detection range of AMR effect is always decided by the saturation field of the hard axis [7,8]. However, due to its soft magnetic properties, the detection range of this kind of AMR was limited. Published works and AMR product datasheets have shown that the detection ranges of AMRs are less than 20 Gs [3,9–11]. In recent years, numerous works have focused on increasing the AMR value through various approaches, such as the use of different buffer layers and the identification and optimization of deposition conditions. The AMR effect of the NiFe film currently approaches 5%
⁎
[3,12–14]. The AMR effect could be applied over a wide field if its detection range can surpass the limit of 20 Gs. The exchange bias (EB) phenomenon was discovered by Meiklejohn and Bean more than 60 years ago [15,16]. It occurs through the interfacial coupling of a ferromagnet (FM) with an antiferromagnet (AFM). Magnetization along the orthogonal direction to the EB field involves coherent rotation when an external magnetic field is applied perpendicular to the EB field. This effect makes it be suitable for sensing [17]. Furthermore, the hard axis saturation field of EB films can be modulated by the EB field Hex [17,18]. This phenomenon enables the tuning of the detection range. However, the intensity of exchange bias field is inversely proportional to the thickness FM layer, and the AMR effect decreases rapidly as magnetic thickness decrease [16,19,20]. An intense EB effect cannot be achieved in a thick magnetic layer. Therefore, the ability to tune the saturation field in a single FM/AFM structure is limited by its small Hex. In our present work, we applied a [FM/AFM]n multilayer and fixed the total thickness of the magnetic film at a relative thick range to obtain a large AMR. The thickness of each magnetic layer, however, could be reduced to improve the EB effect. Therefore, a strong AMR effect and tunable EB field can be achieved for detection range modulation. 2. Experimental The studied sets of AMR multilayer were deposited onto Si substrates at room temperature by using an LS500 automatic system. The nominal composition and thickness (in nm) of the samples were Si/Ta (10)/FeMn (12)/[NiFe (x)/FeMn (12)]n/Ta (10). A bottom FeMn
Corresponding author. E-mail address: [email protected] (X. Tang).
https://doi.org/10.1016/j.jmmm.2019.01.012 Received 19 October 2018; Received in revised form 21 December 2018; Accepted 4 January 2019 Available online 04 January 2019 0304-8853/ © 2019 Elsevier B.V. All rights reserved.
Journal of Magnetism and Magnetic Materials 476 (2019) 469–471
X. Tang et al.
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Fig. 2. Normalized magnetic hysteresis curves measured along (a) the easy, and (b) the hard axis of Si/Ta (10 nm)/FeMn (12 nm)/[NiFe (x nm)/FeMn (12 nm)]n/Ta (10 nm) multilayer. The inset present the exchange bias and saturation fields of the samples.
Fig. 1. (a) Normalized loops measured along the easy and hard axis, and (b) AMR value of NiFe (180 nm) film.
(12 nm) film was deposited to confirm each NiFe layer pinned by a bottom and top AFM layer. The total thickness of NiFe in stack [NiFe/ FeMn]n was fixed at 180 nm, and the number n was changed from 1 to 5. A constant magnetic field of 300 Gs was applied along the substrate during film growth to develop EB. During deposition, the base vacuum was better than 8 × 10−6 Pa. The magnetization measurements were performed in a BHV-525 vibrating sample magnetometer (VSM). The AMR measurements were obtained by means of a standard four-probe configuration with the measuring magnetic field along the hard axis (perpendicular to the deposition field). The DC current of 1 mA was supplied by a current source and applied along the samples’ easy axis (parallel to the deposition field). The voltage produced on the sample was measured with a voltmeter.
magnetic property. The coercive fields of easy axis Hce and hard axis Hch were only 2.3 and 1.3 Gs, respectively. The saturation field (Hs), measured along the hard axis was 9.5 Gs. The AMR curve displayed in Fig. 1(b) shows that the detection range of the film is from −7 to 7.2 Gs. Here, we defined the detection range as the AMR value decreased by 90%. We found that the detection range of AMR was limited by its Hs. These observations are consistent with the results reported by other groups [12–14]. In the following, we obtained a tunable AMR by growing a set of samples of Si/Ta (10 nm)/FeMn (12 nm)/[NiFe (x nm)/FeMn (12 nm)]n/Ta (10 nm) films, where the total thickness of NiFe was fixed at 180 nm. The number of n was changed from 1 to 5, and the thickness of each NiFe layer in the five samples were set as 180, 90, 60, 45, and 36 nm. The hysteresis loops of the films measured along the easy and hard axis are shown in Fig. 2. As illustrated by the easy axis magnetic curves shown in Fig. 2(a), the Hex decreased as the thickness of the NiFe layer increased. This relationship is a typical property of EB effect and indicates that the EB field is inversely proportional to a pinned FM layer. The thickness of the NiFe layer was 180 nm when n = 1. Thus, its Hex was very low, and its magnitude was only 6.2 Gs. However, by increasing n to 5 and
3. Results and discussion For comparison, a NiFe (180 nm) single film without a pinning layer was first deposited. The hysteresis loops along the easy and hard axes of the film are presented in Fig. 1(a), and the response curves of the AMR value under an applied field along the hard axis are displayed in Fig. 1(b). It is obviously that the NiFe film displayed an excellent soft 470
Journal of Magnetism and Magnetic Materials 476 (2019) 469–471
X. Tang et al.
2.5 2.0
n=1
n=2
n=3
n=4
sensitivities. When the detection rage is large, the sensitivity is small [23]. Wide detection range and high sensitivity cannot be obtained simultaneously. Therefore, compromises between detection range and sensitivity are required in practical application, and the appropriate thickness of the [FM/AFM]n stack is selected to meet requirements.
n=5
single NiFe layer
AMR(%)
1.5
4. Conclusions This work investigated the use of a [FM/AFM]n multilayer to achieve the AMR effect with tunable detection range. The detection range of the samples can be easily modulated over a wide range by changing the thickness of each magnetic film in the multilayered structure. The tunability of the detection range is attributed to the change of the saturation field along the hard axis by EB effect. Thus, this multilayered structure could promote AMR sensor applications.
1.0 0.5 0.0 -200
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0
100
200
Acknowledgements
H(Gs) This work was supported by the National Natural Science Foundation of China under Grant Nos. 61471096 and 51772047, and Science and Technology Department of Sichuan Province under Grant Nos. 2016JQ0016 and 2015JQ0031.
Fig. 3. AMR curves of Si/Ta (10 nm)/FeMn (12 nm)/[NiFe (x nm)/FeMn (12 nm)]n/Ta (10 nm) thin films and single NiFe layer.
decreasing the thickness of each NiFe layer to 36 nm, the EB field increased to 41.5 Gs. The hard axis magnetization curves are displayed in Fig. 2(b). They were almost reversible in the entire measure field range. Furthermore, the response is linear in a more restricted field window. In addition, the magnitude of saturation field HS, which was measured along the hard axis, is proportional to the magnitude of Hex. It is gradually strengthened with the decrease in the thickness of the NiFe layer because the EB fields had strengthened [17,18]. The detection range of the AMR effect is related to the saturation field along the hard axis. Therefore, the detection range could be tuned if the EB field could be modulated. In Fig. 3, the AMR response curves are shown. The detection range of the Si/Ta (10 nm)/FeMn (12 nm)/[NiFe (x nm)/FeMn (12 nm)]n/Ta (10 nm) stacks had increased from 20.5 Gs to 116 Gs. As expected, the detection range was easily modulated over a large magnetic field range by varying the EB field values. We also find that although the AMR value for n = 1 was almost the same as that of the single NiFe sample without an AFM layer, the detection range of n = 1 was already twice that of the single NiFe sample. These results indicate that even the EB field is very small in relative thick magnetic film, it is still useful for modulating the detection range without the loss of AMR effect. In addition, the AMR value decrease a little is also observed when the detection range expands. This result accounts for the current shunting effect of the AFM layer. AFM layer is a metal. The current may not fully flow through all the NiFe layer and result in AMR decrease [21,22]. Moreover, the AMR effect decreased as the thickness of the magnetic film decreased. Although the total thickness of NiFe layer in our sample is fixed, the thickness of each FM layer decreased as the period increased. This is another reason for the reducing in the AMR effect. In addition, multilayered AMRs have more interfaces than normal AMR structures. The scattering effect at the interfaces is also the important reason for the reduction in AMR value. The strong scattering of electrons lead to weaken the AMR value [3]. By the way, the detection range of magnetic sensors are inversely proportional to their
References [1] T.R. McGuire, R.I. Potter, IEEE Trans. Magn. 11 (1975) 1018–1038. [2] M. Carlos, C. Carolina, M. Alberto, G. Alfonso, G. Mercedes, Sensors 15 (2015) 28340–28366. [3] W. Shuyun, G. Tiejun, W. Cuntao, H. Jianfang, J. Alloy Compd. 554 (2013) 405–407. [4] I. Mateos, J. Ramos-Castro, A. Lobo, Sens. Actuators A 235 (2015) 57–63. [5] J. Huangfu, S. Sheng, B. Li, G. Yu, Mater. Chin. 30 (2011) 14–21. [6] L. Ding, J. Teng, C. Feng, L. Wei, L. Min, Z. Min, Y. Guanghua, X. Daoping, J. Phys. D: Appl. Phys. 44 (2011) 385001. [7] O.E. da Silva, J.V. de Siqueira, P.R. Kern, W.J.S. Garcia, F. Beck, J.N. Rigue, M. Carara, J. Magn. Magn. Mater. 451 (2018) 507–514. [8] T. Lin, D. Mauri, B. York, P.M. Rice, Appl. Phys. Lett. 84 (2004) 386–388. [9] Y.F. Liu, J.W. Cai, L. Sun, Appl. Phys. Lett. 96 (2010) 092509. [10] Datasheet: 1- and 2-Axis Magnetic Sensors HMC1001/1002/1021/1022, https:// aerospace.honeywell.com/en/products/navigation-and-sensors/low-field-highprecision-linear-1-and-2-axis-analog-magnetic-sensors. [11] D. Lei, T. Jiao, Z. Qian, F. Chun, L. Ming-hua, H. Gang, W. Li-jin, Y. Guang-hua, W. Shu-yun Wang, Appl. Phys. Lett. 94 (2009) 162506. [12] L. Minghua, S. Hui, D. Yuegang, D. Lei, H. Gang, Z. Yao, L. Ye, Y. Guanghua, J. Magn. Magn. Mater. 439 (2017) 17–21. [13] Z. Chong-Jun, L. Yang Liu, Z. Jing-Yan Zhang, S. Li Sun, D. Lei, Z. Peng, W. Bao-Yi, C. Xing-Zhong, Yu. Guang-Hua, Appl. Phys. Lett. 101 (2012) 072404. [14] W.Y. Lee, M.F. Toney, D. Mauri, IEEE Trans. Magn. 36 (2000) 381–385. [15] W.P. Meiklejohn, C.P. Bean, Phys. Rev. 102 (1956) 1413–1414. [16] J. Noguésa, J. Sorta, V. Langlaisb, V. Skumryeva, S. Suriñachb, J.S. Muñozb, M.D. Barób, Phys. Rep. 422 (2005) 65–117. [17] T. XiaoLi Tang, Y. You, L. Ru, S. Hua, Z. HuaiWu, Z. ZhiYong, J. YuLan, J. Magn. Magn. Mater. 429 (2017) 65–68. [18] G. Malinowski, M. Hehn, M. Sajieddine, F. Montaigne, E. Jouguelet, F. Canet, M. Alnot, D. Lacour, A. Schuh, Appl. Phys. Lett. 83 (2003) 4372. [19] T.R. McGuire, R.I. Potter, IEEE Trans. Magn. 29 (1975) 1018–1038. [20] T. XiaoLi, Z. HuaiWu, S. Hua, Z. ZhiYong, J. YuLan, J. Magn. Magn. Mater. 312 (2007) 366–369. [21] B. Kocaman, N. Akdogan, J. Magn. Magn. Mater. 456 (2018) 17–21. [22] D.V. Dimitrov, D. Song, M.W. Covington, Tuned shunt ratio for magnetic sensors, Google Patents, 2014. [23] B. Negulescu, D. Lacour, F. Montaigne, A. Gerken, J. Paul, V. Spetter, J. Marien, C. Duret, M. Hehn, Appl. Phys. Lett. 95 (2009) 112502.
471
Contents lists available at ScienceDirect
Journal of Magnetism and Magnetic Materials journal homepage: www.elsevier.com/locate/jmmm
Research articles
A flexible way to modulate the detection range of anisotropic magnetoresistance by exchange bias field
T
⁎
XiaoLi Tang , Wei Du, JinBiao Yu, HuaiWu Zhang, Hua Su State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, Sichuan 610054, China
A B S T R A C T
A series of Ta/FeMn/[NiFe/FeMn]n/Ta films was grown through DC-sputtering. They acted as a new structure of multilayer anisotropic magnetoresistance (AMR). Based on the exchange bias (EB) field producing at the NiFe/FeMn interface, the linear range and saturation field along the multilayer’s hard axis enlarged when compared with a single NiFe layer. The linear range and saturation field decided the detection range of the AMR. Therefore, by fixing the total thickness of magnetic NiFe layer and selecting different number of n in multilayer, each thickness of NiFe layer was changed to tune EB field. Then, the detection range was modulated by varying exchange bias fields. Adopting this method, the detection range could be easy to control and adjustable from 20.5 Gs to 116 Gs on the basis of AMR responses. The proposed method promotes the application of the AMR effect over a wide magnetic detection area.
1. Introduction The anisotropic magnetoresistance (AMR) effect, which originates from the anisotropic scattering of conduction electrons due to spin–orbit interactions, has been extensively studied over the past few decades. The application of AMR thin films as magnetic sensors and detectors has been proposed because their resistance varies under magnetic fields [1–3]. Although the magnetoresistance effects of newly discovered giant magnetoresistance and tunneling magnetoresistance are more intense than those of AMR, the AMR effect can be achieved with only one magnetic layer. Given this advantage, AMR structures are simple and easy to fabricate and integrate. Therefore, AMR sensors are in high demands for applications in information processing, automation, and navigation, as well as military fields [4–6]. NiFe permalloy is the best material for use in AMR devices because of its high AMR amplitude and sensitivity and low cost. In magnetic detection, linearity and reversibility require the coherent rotation of magnetization under the detection direction. The sensitive direction or detection field is always along the hard layer of the magnetic film to meet this requirement. Therefore, the detection range of AMR effect is always decided by the saturation field of the hard axis [7,8]. However, due to its soft magnetic properties, the detection range of this kind of AMR was limited. Published works and AMR product datasheets have shown that the detection ranges of AMRs are less than 20 Gs [3,9–11]. In recent years, numerous works have focused on increasing the AMR value through various approaches, such as the use of different buffer layers and the identification and optimization of deposition conditions. The AMR effect of the NiFe film currently approaches 5%
⁎
[3,12–14]. The AMR effect could be applied over a wide field if its detection range can surpass the limit of 20 Gs. The exchange bias (EB) phenomenon was discovered by Meiklejohn and Bean more than 60 years ago [15,16]. It occurs through the interfacial coupling of a ferromagnet (FM) with an antiferromagnet (AFM). Magnetization along the orthogonal direction to the EB field involves coherent rotation when an external magnetic field is applied perpendicular to the EB field. This effect makes it be suitable for sensing [17]. Furthermore, the hard axis saturation field of EB films can be modulated by the EB field Hex [17,18]. This phenomenon enables the tuning of the detection range. However, the intensity of exchange bias field is inversely proportional to the thickness FM layer, and the AMR effect decreases rapidly as magnetic thickness decrease [16,19,20]. An intense EB effect cannot be achieved in a thick magnetic layer. Therefore, the ability to tune the saturation field in a single FM/AFM structure is limited by its small Hex. In our present work, we applied a [FM/AFM]n multilayer and fixed the total thickness of the magnetic film at a relative thick range to obtain a large AMR. The thickness of each magnetic layer, however, could be reduced to improve the EB effect. Therefore, a strong AMR effect and tunable EB field can be achieved for detection range modulation. 2. Experimental The studied sets of AMR multilayer were deposited onto Si substrates at room temperature by using an LS500 automatic system. The nominal composition and thickness (in nm) of the samples were Si/Ta (10)/FeMn (12)/[NiFe (x)/FeMn (12)]n/Ta (10). A bottom FeMn
Corresponding author. E-mail address: [email protected] (X. Tang).
https://doi.org/10.1016/j.jmmm.2019.01.012 Received 19 October 2018; Received in revised form 21 December 2018; Accepted 4 January 2019 Available online 04 January 2019 0304-8853/ © 2019 Elsevier B.V. All rights reserved.
Journal of Magnetism and Magnetic Materials 476 (2019) 469–471
X. Tang et al.
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Fig. 2. Normalized magnetic hysteresis curves measured along (a) the easy, and (b) the hard axis of Si/Ta (10 nm)/FeMn (12 nm)/[NiFe (x nm)/FeMn (12 nm)]n/Ta (10 nm) multilayer. The inset present the exchange bias and saturation fields of the samples.
Fig. 1. (a) Normalized loops measured along the easy and hard axis, and (b) AMR value of NiFe (180 nm) film.
(12 nm) film was deposited to confirm each NiFe layer pinned by a bottom and top AFM layer. The total thickness of NiFe in stack [NiFe/ FeMn]n was fixed at 180 nm, and the number n was changed from 1 to 5. A constant magnetic field of 300 Gs was applied along the substrate during film growth to develop EB. During deposition, the base vacuum was better than 8 × 10−6 Pa. The magnetization measurements were performed in a BHV-525 vibrating sample magnetometer (VSM). The AMR measurements were obtained by means of a standard four-probe configuration with the measuring magnetic field along the hard axis (perpendicular to the deposition field). The DC current of 1 mA was supplied by a current source and applied along the samples’ easy axis (parallel to the deposition field). The voltage produced on the sample was measured with a voltmeter.
magnetic property. The coercive fields of easy axis Hce and hard axis Hch were only 2.3 and 1.3 Gs, respectively. The saturation field (Hs), measured along the hard axis was 9.5 Gs. The AMR curve displayed in Fig. 1(b) shows that the detection range of the film is from −7 to 7.2 Gs. Here, we defined the detection range as the AMR value decreased by 90%. We found that the detection range of AMR was limited by its Hs. These observations are consistent with the results reported by other groups [12–14]. In the following, we obtained a tunable AMR by growing a set of samples of Si/Ta (10 nm)/FeMn (12 nm)/[NiFe (x nm)/FeMn (12 nm)]n/Ta (10 nm) films, where the total thickness of NiFe was fixed at 180 nm. The number of n was changed from 1 to 5, and the thickness of each NiFe layer in the five samples were set as 180, 90, 60, 45, and 36 nm. The hysteresis loops of the films measured along the easy and hard axis are shown in Fig. 2. As illustrated by the easy axis magnetic curves shown in Fig. 2(a), the Hex decreased as the thickness of the NiFe layer increased. This relationship is a typical property of EB effect and indicates that the EB field is inversely proportional to a pinned FM layer. The thickness of the NiFe layer was 180 nm when n = 1. Thus, its Hex was very low, and its magnitude was only 6.2 Gs. However, by increasing n to 5 and
3. Results and discussion For comparison, a NiFe (180 nm) single film without a pinning layer was first deposited. The hysteresis loops along the easy and hard axes of the film are presented in Fig. 1(a), and the response curves of the AMR value under an applied field along the hard axis are displayed in Fig. 1(b). It is obviously that the NiFe film displayed an excellent soft 470
Journal of Magnetism and Magnetic Materials 476 (2019) 469–471
X. Tang et al.
2.5 2.0
n=1
n=2
n=3
n=4
sensitivities. When the detection rage is large, the sensitivity is small [23]. Wide detection range and high sensitivity cannot be obtained simultaneously. Therefore, compromises between detection range and sensitivity are required in practical application, and the appropriate thickness of the [FM/AFM]n stack is selected to meet requirements.
n=5
single NiFe layer
AMR(%)
1.5
4. Conclusions This work investigated the use of a [FM/AFM]n multilayer to achieve the AMR effect with tunable detection range. The detection range of the samples can be easily modulated over a wide range by changing the thickness of each magnetic film in the multilayered structure. The tunability of the detection range is attributed to the change of the saturation field along the hard axis by EB effect. Thus, this multilayered structure could promote AMR sensor applications.
1.0 0.5 0.0 -200
-100
0
100
200
Acknowledgements
H(Gs) This work was supported by the National Natural Science Foundation of China under Grant Nos. 61471096 and 51772047, and Science and Technology Department of Sichuan Province under Grant Nos. 2016JQ0016 and 2015JQ0031.
Fig. 3. AMR curves of Si/Ta (10 nm)/FeMn (12 nm)/[NiFe (x nm)/FeMn (12 nm)]n/Ta (10 nm) thin films and single NiFe layer.
decreasing the thickness of each NiFe layer to 36 nm, the EB field increased to 41.5 Gs. The hard axis magnetization curves are displayed in Fig. 2(b). They were almost reversible in the entire measure field range. Furthermore, the response is linear in a more restricted field window. In addition, the magnitude of saturation field HS, which was measured along the hard axis, is proportional to the magnitude of Hex. It is gradually strengthened with the decrease in the thickness of the NiFe layer because the EB fields had strengthened [17,18]. The detection range of the AMR effect is related to the saturation field along the hard axis. Therefore, the detection range could be tuned if the EB field could be modulated. In Fig. 3, the AMR response curves are shown. The detection range of the Si/Ta (10 nm)/FeMn (12 nm)/[NiFe (x nm)/FeMn (12 nm)]n/Ta (10 nm) stacks had increased from 20.5 Gs to 116 Gs. As expected, the detection range was easily modulated over a large magnetic field range by varying the EB field values. We also find that although the AMR value for n = 1 was almost the same as that of the single NiFe sample without an AFM layer, the detection range of n = 1 was already twice that of the single NiFe sample. These results indicate that even the EB field is very small in relative thick magnetic film, it is still useful for modulating the detection range without the loss of AMR effect. In addition, the AMR value decrease a little is also observed when the detection range expands. This result accounts for the current shunting effect of the AFM layer. AFM layer is a metal. The current may not fully flow through all the NiFe layer and result in AMR decrease [21,22]. Moreover, the AMR effect decreased as the thickness of the magnetic film decreased. Although the total thickness of NiFe layer in our sample is fixed, the thickness of each FM layer decreased as the period increased. This is another reason for the reducing in the AMR effect. In addition, multilayered AMRs have more interfaces than normal AMR structures. The scattering effect at the interfaces is also the important reason for the reduction in AMR value. The strong scattering of electrons lead to weaken the AMR value [3]. By the way, the detection range of magnetic sensors are inversely proportional to their
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