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

doi:10.1088/1674-1056/19/6/067504

Abstract This paper reports that the SmCo_6.8Zr_0.2 nanocrystalline permanent magnets and SmCo_6.8Zr_0.2/$\alpha$-(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 SmCo_6.8Zr_0.2 nanocrystalline permanent magnets is composed of SmCo₇ phase and SmCo_6.8Zr_0.2/$\alpha$-(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 SmCo_6.8Zr_0.2 and SmCo_6.8Zr_0.2/$\alpha$-(Fe,Co) magnets. The inter-grain exchange interaction at low temperature is investigated, which shows that the inter-grain exchange interaction of SmCo_6.8Zr_0.2/$\alpha$-(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 SmCo_6.8Zr_0.2 and SmCo_6.8Zr_0.2/$\alpha$-(Fe,Co) magnets with the decreasing temperature are analysed in detail. The magnetic viscosity and the activation volume of SmCo_6.8Zr_0.2 and SmCo_6.8Zr_0.2/$\alpha$-(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

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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 SmCo_6.8Zr_0.2 and SmCo_6.8Zr_0.2/$\alpha$ -(Fe,Co) nanocrystalline magnets at low temperature 2010 Chin. Phys. B 19 067504

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

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The magnetization reversal behaviour for SmCo_6.8Zr_0.2 and SmCo_6.8Zr_0.2/$\alpha$ -(Fe,Co) nanocrystalline magnets at low temperature