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In this paper, the nanocomposites are synthesized by the non-equal precipitation method to study the effect of the metal ions doped in antiferromagnetic matrix on the exchange bias. XRD patterns and SEM images reveal that the as-synthesized CuO nanocomposites have uniform size (～80 nm), and the ferrimagnetic particles MFe2O4 (M=Cu, Ni) are embedded in the antiferromagnetic (AFM) CuO matrix by doping of magnetic metal ions Ni and Fe. And the ferrimagnetic phase MFe2O4 (M=Cu, Ni) is formed through the addition of a small amount of Fe that reacts with Cu and Ni ions. Effects of different doping amount of Ni on exchange bias are different. A small doping amount of Ni can induce magnetic disorder at the interface of both phases, then the spin-glass-like phase may be formed. The spin-glass-like phases enhance the pinning effect on the magnetic moments of ferrimagnetic phase. Meanwhile, during field cooling process the antiferromagnetic phase splits into domains, which are aligned either with cooling field or in the original antiferromagnetic configuration. The domain wall serves as pinning sites for the magnetic moments of ferromagnetic phase, and the exchange bias effect is increased. The AFM NiO grains with high anisotropic energy are generated, this also increases the exchange bias effect when continuous doping of Ni ions. In the process of field cooling (FC), upward shift occurs in all hysteresis loops, which is perpendicular to the exchange bias. As x=0.08 (x is the concentration of Ni) the perpendicular displacement is 3.6%, this behavior also proves that under FC measurements, the spin-glass-like phase can be formed between the antiferromagnetic nanopaticles. It is the magnetic exchange coupling at the interface between the ferrimagnetic phase and the spin-glass-like phase that result in an upward shift in the entire measurement range. The plot of M versus T under zero field cooling (ZFC) and field cooling (FC) indicates that the exchange bias effect in these composites is ascribed to the exchange coupling at the interface between the ferrimagnetic particles and the spin-glass-like phase. With continuous introduction of magnetic Ni ions, the exchange bias field first increases slowly, then at x=0.08 it increases sharply. The existence of AFM NiO with high anisotropic energy and the domain structure in AFM matrix are the causes of the result.
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Keywords:
- doping /
- exchange bias /
- ferrimagnetic /
- antiferromagnetic
[1] Zhao F, Qiu H M, Pan L Q 2008 J. Phys.:Condens. Matter 20 425208
[2] Zheng R K, Liu H, Zhang X X, Roy V A L, Djuriši A B2004 Appl. Phys. Lett. 85 2589
[3] L Q R, Fang Q Q, Liu Y M 2011 Acta Phys. Sin. 60 047501 (in Chinese) [吕清荣, 方庆清, 刘艳美 2011 60 047501]
[4] Kumar P K, Mandal K 2007 J. Appl. Phys. 101 113906
[5] Nogués J, Sort J, Langlais V 2005 Physics Reports 422 65
[6] Meiklejohn W H, Bean C P 1956 Phys. Rev. 105 904
[7] Kodama R H, Berkowitz A E 1999 Phys. Rev. B 59 6321
[8] Luo Y, Zhao G P, Yang H T, Shong N N, Ren X, Ding H F, Cheng Z H 2013 Acta Phys. Sin. 62 176102 (in Chinese) [罗毅, 赵国平, 杨海涛, 宋宁宁, 任肖, 丁浩峰, 成昭华 2013 62 176102]
[9] Carpenter R, Vallejo-Fernandez G, Apos K O, Grady 2014 J. Appl. Phys. 115 17D715
[10] Dogan Kaya, Pavel N. L, Priyanga Jayathilaka, Hillary Kirby, Casey W. M, Roshchin I V 2013 J. Appl. Phys. 113 17D717
[11] Kosub T, Bachmatiuk A, Makarov D, Baunack S, Neu V, Wolter A, Rmmeli M H, Schmidt O G 2012 J. Appl. Phys. 112 123917
[12] Ma Z Z, Li J Q, Chen Z P, Tian Z B, Hu X J, Hang H J 2014 Chin. Phyc. B 23 097505
[13] Dai B, Lei Y, Shao X P, Ni J 2010 J. Alloys Compd. 490 427
[14] Shi Z, Du j, Zhou S M 2014 Chin. Phyc. B 23 027503
[15] Òscar I, Xavier B, Amílcar L 2008 J. Phys. D: Appl. Phys. 41 134010
[16] Karmakar S, Taran S, Bose E, Chaudhuri B K 2008 Phys. Rev. B 77 144409
[17] Passamani E C, Larica C, Marques C, Takeuchi A Y, Proveti J R, Favre-Nicolin E 2007 J. Magn. Magn. Mater. 314 21
[18] Punnoose A, Seehra M S 2002 J. Appl. Phys. 91 7766
[19] Leighton C, Nogués J, Jönsson-Åkerman B J, Schuller Ivan K 2000 Appl. Phys. Lett. 84 3466
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[1] Zhao F, Qiu H M, Pan L Q 2008 J. Phys.:Condens. Matter 20 425208
[2] Zheng R K, Liu H, Zhang X X, Roy V A L, Djuriši A B2004 Appl. Phys. Lett. 85 2589
[3] L Q R, Fang Q Q, Liu Y M 2011 Acta Phys. Sin. 60 047501 (in Chinese) [吕清荣, 方庆清, 刘艳美 2011 60 047501]
[4] Kumar P K, Mandal K 2007 J. Appl. Phys. 101 113906
[5] Nogués J, Sort J, Langlais V 2005 Physics Reports 422 65
[6] Meiklejohn W H, Bean C P 1956 Phys. Rev. 105 904
[7] Kodama R H, Berkowitz A E 1999 Phys. Rev. B 59 6321
[8] Luo Y, Zhao G P, Yang H T, Shong N N, Ren X, Ding H F, Cheng Z H 2013 Acta Phys. Sin. 62 176102 (in Chinese) [罗毅, 赵国平, 杨海涛, 宋宁宁, 任肖, 丁浩峰, 成昭华 2013 62 176102]
[9] Carpenter R, Vallejo-Fernandez G, Apos K O, Grady 2014 J. Appl. Phys. 115 17D715
[10] Dogan Kaya, Pavel N. L, Priyanga Jayathilaka, Hillary Kirby, Casey W. M, Roshchin I V 2013 J. Appl. Phys. 113 17D717
[11] Kosub T, Bachmatiuk A, Makarov D, Baunack S, Neu V, Wolter A, Rmmeli M H, Schmidt O G 2012 J. Appl. Phys. 112 123917
[12] Ma Z Z, Li J Q, Chen Z P, Tian Z B, Hu X J, Hang H J 2014 Chin. Phyc. B 23 097505
[13] Dai B, Lei Y, Shao X P, Ni J 2010 J. Alloys Compd. 490 427
[14] Shi Z, Du j, Zhou S M 2014 Chin. Phyc. B 23 027503
[15] Òscar I, Xavier B, Amílcar L 2008 J. Phys. D: Appl. Phys. 41 134010
[16] Karmakar S, Taran S, Bose E, Chaudhuri B K 2008 Phys. Rev. B 77 144409
[17] Passamani E C, Larica C, Marques C, Takeuchi A Y, Proveti J R, Favre-Nicolin E 2007 J. Magn. Magn. Mater. 314 21
[18] Punnoose A, Seehra M S 2002 J. Appl. Phys. 91 7766
[19] Leighton C, Nogués J, Jönsson-Åkerman B J, Schuller Ivan K 2000 Appl. Phys. Lett. 84 3466
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