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Chin. Phys. B, 2010, Vol. 19(6): 067504    DOI: 10.1088/1674-1056/19/6/067504

The magnetization reversal behaviour for SmCo6.8Zr0.2 and SmCo6.8Zr0.2/$\alpha$ -(Fe,Co) nanocrystalline magnets at low temperature

Liu Zhuang(刘壮)a)b)†, Chen Ren-Jie(陈仁杰)a), Li Dong(李东)a), and Yan Ar-Ru(闫阿儒)a)
a Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology, Ningbo Institute of Material Technology \& Engineering, Chinese Academy of Sciences, Ningbo 315201, China; b Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031, China
Abstract  This paper reports that the SmCo6.8Zr0.2 nanocrystalline permanent magnets and SmCo6.8Zr0.2/$\alpha$-(Fe,Co) nanocomposite permanent magnets are successfully produced by mechanical alloying and subsequently annealing at 700 ${^\circ}$C for 10 minutes. The x-ray diffraction results show that the phase structure of SmCo6.8Zr0.2 nanocrystalline permanent magnets is composed of SmCo7 phase and SmCo6.8Zr0.2/$\alpha$-(Fe, Co) nanocomposite permanent magnets is composed of SmCo7 and $\alpha$ -(Fe,Co) phases. The mechanism of magnetization reversal is mainly controlled by inhomogeneous domain wall pinning in SmCo6.8Zr0.2 and SmCo6.8Zr0.2/$\alpha$-(Fe,Co) magnets. The inter-grain exchange interaction at low temperature is investigated, which shows that the inter-grain exchange interaction of SmCo6.8Zr0.2/$\alpha$-(Fe,Co) magnets increases greatly by the decrease of the measured temperature. According to $\Delta m_{\rm irr}-H/H_{\rm cj}$, $\Delta m_{\rm rev}-H/H_{\rm cj}$ and $\chi_{\rm irr}-H/H_{\rm cj}$ curves at room temperature and 100 K, the changes of irreversible and reversible magnetization behaviours of SmCo6.8Zr0.2 and SmCo6.8Zr0.2/$\alpha$-(Fe,Co) magnets with the decreasing temperature are analysed in detail. The magnetic viscosity and the activation volume of SmCo6.8Zr0.2 and SmCo6.8Zr0.2/$\alpha$-(Fe,Co) magnets at different temperatures are also studied.
Keywords:  nanocrystalline magnets      coercivity mechanism      inter-grain exchange coupling      magnetization reversal behaviour  
Received:  09 October 2009      Accepted manuscript online: 
PACS:  75.60.Jk (Magnetization reversal mechanisms)  
  75.50.Tt (Fine-particle systems; nanocrystalline materials)  
  75.50.Ww (Permanent magnets)  
  81.16.-c (Methods of micro- and nanofabrication and processing)  
  75.60.Ch (Domain walls and domain structure)  
  75.60.Lr (Magnetic aftereffects)  
Fund: Project supported by the Natural Science Foundation of Zhejiang Province of China (Grant No.~Y407174), Major Scientific and Technological Special Fund of Zhejiang Province of China (Grant No.~2007C11046) and the National Basic Research Program of China (G

Cite this article: 

Liu Zhuang(刘壮), Chen Ren-Jie(陈仁杰), Li Dong(李东), and Yan Ar-Ru(闫阿儒) The magnetization reversal behaviour for SmCo6.8Zr0.2 and SmCo6.8Zr0.2/$\alpha$ -(Fe,Co) nanocrystalline magnets at low temperature 2010 Chin. Phys. B 19 067504

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