Large cryogenic magnetocaloric effect in the blocking state of GdAl(2)/Al(2)O(3) nanocapsules

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	Large cryogenic magnetocaloric effect in the blocking state of GdAl(2)/Al(2)O(3) nanocapsules
	S. Ma; W. F. Li; D. Li; D. K. Xiong; N. K. Sun; D. Y. Geng; W. Liu; Z. D. Zhang
	2007
发表期刊	Physical Review B
ISSN	1098-0121
卷号	76 期号:14
摘要	The nanocapsules with crystalline cores of GdAl(2) compound and shells of amorphous Al(2)O(3) were prepared by evaporating Gd(x)Al(100-x) (x=50, 60, 70, 80, and 90) alloys using a modified arc-discharge technique. The morphologies, average sizes, lattice constants, and surface characteristics of GdAl(2)/Al(2)O(3) nanocapsules were studied in detail by means of x-ray diffraction, energy dispersive spectroscopy, x-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy. The formation mechanism of the nanocapsules was analyzed in detail. The differences in Curie temperatures and anisotropy constants of these nanocapsules were discussed with respect to their different structural characteristics. From 180 to 5 K, the magnetic entropy change of the GdAl(2)/Al(2)O(3) nanocapsules continuously increases with decreasing temperature T and rapidly enhances when the temperature tends to 5 K. The largest entropy change -Delta S at 7.5 K can respectively reach 18.02, 18.71, and 31.01 J kg(-1) K(-1) by varying the magnetic field from 7 to 1 T for the nanocapsules synthesized by arc-discharging Gd(70)Al(30), Gd(80)Al(20), and Gd(90)Al(10) alloys. The appearance of a large entropy change at low temperatures was ascribed to a lower anisotropy energy barrier and a high magnetic-moment density of the nanocapsules. The linear relation between the magnetic entropy change and the reciprocal of the temperature (1/T) was discussed in terms of superparamagnetism and magnetocaloric theory.
部门归属	[ma, s.; li, w. f.; li, d.; xiong, d. k.; sun, n. k.; geng, d. y.; liu, w.; zhang, z. d.] chinese acad sci, int ctr mat phys, shenyang natl lab mat sci, shenyang 110016, peoples r china.;ma, s (reprint author), chinese acad sci, int ctr mat phys, shenyang natl lab mat sci, 72 wenhua rd, shenyang 110016, peoples r china
关键词	Magnetic Entropy Change Fe-co(c) Nanocapsules Arc-discharge Iron-oxide Gdal2 Nanoparticles Particles Nanocomposites Refrigeration Polarization
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文献类型	期刊论文
条目标识符	http://ir.imr.ac.cn/handle/321006/33752
专题	中国科学院金属研究所
推荐引用方式 GB/T 7714	S. Ma,W. F. Li,D. Li,et al. Large cryogenic magnetocaloric effect in the blocking state of GdAl(2)/Al(2)O(3) nanocapsules[J]. Physical Review B,2007,76(14).
APA	S. Ma.,W. F. Li.,D. Li.,D. K. Xiong.,N. K. Sun.,...&Z. D. Zhang.(2007).Large cryogenic magnetocaloric effect in the blocking state of GdAl(2)/Al(2)O(3) nanocapsules.Physical Review B,76(14).
MLA	S. Ma,et al."Large cryogenic magnetocaloric effect in the blocking state of GdAl(2)/Al(2)O(3) nanocapsules".Physical Review B 76.14(2007).