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In the early 1980 s, the soft and hard magnetic nano-two-phase permanent magnet materials were developed and exchange coupling model was put forward. Moreover, the theoretical maximum magnetic energy product could reach 120 MGOe (1 Oe=79.5775 A/m). However a great many of experimental research results are always disappointing for theoretical calculation, but previous studies have shown that there exists also a strong exchange coupling in hard magnetic phase, which can improve the magnetic property of magnet. In this paper, nanocomposite Ta(50 nm)/NdFeB(100 nm)/Ta(2 nm)/NdCeFeB(100 nm)/Ta(2 nm)/NdFeB(100 nm)/Ta(40 nm) multilayer films with Ta underlayers and coverlayers are fabricated on Si substrates by direct current sputtering. A 50 nm Ta underlayer and a 40 nm coverlayer are sputtered at room temperature to align the easy axis of the RE2Fe14B grains to the direction perpendicular to the film plane and to prevent the magnetic film from oxidizing, respectively. The 2 nm Ta spacer layer serves as suppressing the diffusion of elements between different magnetic layers. The NdFeB and NdCeFeB magnetic film are deposited at 630℃ and 610℃, respectively, and then they are followed by in situ rapid thermal annealing at 645-705℃ for 30 min. The microstructures and morphologies of the films are characterized by X-ray diffractometry with Cu K radiation, atomic force microscope, and magnetic force microscope. The magnetic properties of the films are measured with vibrating sample magnetometer. The influences of annealing temperature on magnetic property and crystal structure of the film are investigated. The results show that the magnetic property of the film improves gradually with the increase of annealing temperature, but deteriorates sharply when the temperature reaches above 695℃. When the annealing temperature is 675℃, the coercivity Hci of the film reaches 10.1 kOe and the remanence 4Mr is 5.91 kG (1 G=103/(4) A/m), with a magnetic field applied to the direction perpendicular to the plane of the Nd-Ce-Fe-B thin film. The X-ray diffraction results show that the grains of the hard magnetic phase (2:14:1 phase) grow almost along the substrate normal (c-axis direction), of course, with a certain misorientation. Through the magnetization reversal process of the Nd-Ce-Fe-B thin film, it is found that the minimum value of Mrev moves in the direction of decreasing Mirr as the applied magnetic field increases, which is similar to the domain wall bowing model. This indicates that there is a strong local domain wall pinning in the film. Moreover, the remanence curve shows that the pinning type mechanism is indeed not dominant in the magnetization reversal process of the Nd-Ce-Fe-B thin film after annealing at 685℃. In addition, Henkel plots are also investigated in the films at different annealing temperatures. It is believed that nonzero m is due to the interaction between particles in the magnet. It can be stated based on the measuring results that there exists a strong magnetic exchange coupling effect in the Nd-Ce-Fe-B thin film.
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Keywords:
- permanent magnetic film /
- magnetic properties /
- magnetization reversal /
- exchange coupling
[1] Sagawa M, Togawa N, Yamamoto H, Matsuura Y 1984 J. Appl. Phys. 55 2083
[2] Sato T, Oka N, Ohsuna T, Kaneko Y, Suzuki S, Shima T 2011 J. Appl. Phys. 110 023903
[3] Wang W J, Guo Z H, Li A H, Li X M, Li W 2006 J. Magn. Magn. Mater. 303 392
[4] Zhu M G, Li W, Gao R W, Han G B, Feng W C 2004 Acta Phys. Sin. 53 3171 (in Chinese) [朱明刚, 李卫, 高汝伟, 韩广兵, 冯维存 2004 物理学报 53 3171]
[5] Dai L C, Jian X L, Zhao Y Y, Yao X X, Zhao Z G 2016 Acta Phys. Sin. 65 234101 (in Chinese) [戴存礼, 骞兴亮, 赵艳艳, 姚雪霞, 赵志刚 2016 物理学报 65 234101]
[6] Akdogan O, Dobrynin A, LeRoy D, Dempsey N M, Givord D 2014 J. Appl. Phys. 115 17A764
[7] Herbst J F 1991 Rev. Mod. Phys. 63 819
[8] Zhu M G, Li W, Wang J D, Zheng L Y, Li Y F, Zhang K, Feng H B, Liu T 2013 IEEE Trans. Magn. 50 1000104
[9] Huang S L, Feng H B, Zhu M G, Li A H, Zhang Y, Li W 2014 AIP Adv. 4 107127
[10] Coehoorn R, de Mooij D B, Duchateau J P W B, Buschow K H J 1988 J. Phys. Colloques 49 C8-669
[11] Skomski R, Coey J M D 1993 Phys. Rev. B 48 15812
[12] Leineweber T, Kronmller H J 1997 Magn. Magn. Mater. 176 145
[13] Liu X H, Yan G, Cui L Y, Zhou S X, Zheng W, Wang A L, Chen J C 1999 IEEE Trans. Magn. 35 3331
[14] Feng W C, Li W, Zhu M G, Han G B, Gao R W 2008 Acta Metall. Sin. 44 8 (in Chinese) [冯维存, 李卫, 朱明刚, 韩广兵, 高汝伟 2008 金属学报 44 8]
[15] Ding J, Street R, McCormick P G 1992 J. Magn. Magn. Mater. 115 211
[16] Hadjipanayis G C, Kim A 1988 J. Appl. Phys. 63 3310
[17] Wohlfarth E P 1958 J. Appl. Phys. 29 595
[18] Cammarano R, McCormick P G, Street R 1996 J. Phys. D 29 2327
[19] Livingston J D 1987 IEEE Trans. Magn. MAG-23 2109
[20] Crew D C, McConrmick P G, Street R 1999 J. Appl. Phys. 86 3278
[21] Henkel O 1964 Phys. Stat. Sol. 7 919
[22] Kelly P E, Grady K O, Mayo P I, Chantrell R W 1989 IEEE Trans. Magn. 25 3881
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[1] Sagawa M, Togawa N, Yamamoto H, Matsuura Y 1984 J. Appl. Phys. 55 2083
[2] Sato T, Oka N, Ohsuna T, Kaneko Y, Suzuki S, Shima T 2011 J. Appl. Phys. 110 023903
[3] Wang W J, Guo Z H, Li A H, Li X M, Li W 2006 J. Magn. Magn. Mater. 303 392
[4] Zhu M G, Li W, Gao R W, Han G B, Feng W C 2004 Acta Phys. Sin. 53 3171 (in Chinese) [朱明刚, 李卫, 高汝伟, 韩广兵, 冯维存 2004 物理学报 53 3171]
[5] Dai L C, Jian X L, Zhao Y Y, Yao X X, Zhao Z G 2016 Acta Phys. Sin. 65 234101 (in Chinese) [戴存礼, 骞兴亮, 赵艳艳, 姚雪霞, 赵志刚 2016 物理学报 65 234101]
[6] Akdogan O, Dobrynin A, LeRoy D, Dempsey N M, Givord D 2014 J. Appl. Phys. 115 17A764
[7] Herbst J F 1991 Rev. Mod. Phys. 63 819
[8] Zhu M G, Li W, Wang J D, Zheng L Y, Li Y F, Zhang K, Feng H B, Liu T 2013 IEEE Trans. Magn. 50 1000104
[9] Huang S L, Feng H B, Zhu M G, Li A H, Zhang Y, Li W 2014 AIP Adv. 4 107127
[10] Coehoorn R, de Mooij D B, Duchateau J P W B, Buschow K H J 1988 J. Phys. Colloques 49 C8-669
[11] Skomski R, Coey J M D 1993 Phys. Rev. B 48 15812
[12] Leineweber T, Kronmller H J 1997 Magn. Magn. Mater. 176 145
[13] Liu X H, Yan G, Cui L Y, Zhou S X, Zheng W, Wang A L, Chen J C 1999 IEEE Trans. Magn. 35 3331
[14] Feng W C, Li W, Zhu M G, Han G B, Gao R W 2008 Acta Metall. Sin. 44 8 (in Chinese) [冯维存, 李卫, 朱明刚, 韩广兵, 高汝伟 2008 金属学报 44 8]
[15] Ding J, Street R, McCormick P G 1992 J. Magn. Magn. Mater. 115 211
[16] Hadjipanayis G C, Kim A 1988 J. Appl. Phys. 63 3310
[17] Wohlfarth E P 1958 J. Appl. Phys. 29 595
[18] Cammarano R, McCormick P G, Street R 1996 J. Phys. D 29 2327
[19] Livingston J D 1987 IEEE Trans. Magn. MAG-23 2109
[20] Crew D C, McConrmick P G, Street R 1999 J. Appl. Phys. 86 3278
[21] Henkel O 1964 Phys. Stat. Sol. 7 919
[22] Kelly P E, Grady K O, Mayo P I, Chantrell R W 1989 IEEE Trans. Magn. 25 3881
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