日本語フィールド
著者：X.G. Zheng, H. Kubozono, H. Yamada, K. Kato, Y. Ishiwata, C. N. Xu題名：Giant negative thermal expansion in magnetic nanocrystals発表情報：Nature Nanotechnology 巻: 3 号: 12 ページ: 724-726キーワード：negative thermal expansion, magnetic nanocrystal概要：抄録：Most solids expand when they are heated but a property known as negative thermal expansion (NTE) has been observed in a number of materials, including the oxide ZrW2O8 (1) and the framework material ZnxCd1-x(CN)2 (7, 8). This unusual behaviour can be understood in terms of low-energy phonons (1,2,3,6,7,8), while the colossal values of both positive and negative thermal expansion recently observed in another framework material, Ag3[Co(CN)6], has been explained in terms of the geometric flexibility of its metal-cyanide-metal linkages (9). Thermal expansion can also be stopped in some magnetic transition metal alloys below their magnetic ordering temperature, a phenomenon known as the Invar effect (4,5), and the possibility of exploiting materials with tunable positive or negative thermal expansion in industrial applications has led to intense interest in both the Invar effect and NTE. Here we report the results of thermal expansion experiments on three magnetic nanocrystals – CuO, MnF2 and NiO – and find evidence for NTE in both CuO and MnF2 below their magnetic transition temperatures, but not in NiO. Larger particles of CuO and MnF2 also show prominent magnetostriction (that is, they change shape in response to an applied magnetic field), which results in significantly reduced thermal expansion below their magnetic ordering temperatures [QUERY – are the magnetic ordering temperature and the magnetic transition temperature the same?], whereas this behaviour is not observed in NiO. We propose that the NTE effect in CuO (which is four times larger than that observed in ZrW2O8) and MnF2 is a general property of nanoparticles in which there is strong coupling between [QUERY - please explain magnetolattice coupling in simple terms].英語フィールド
Author：X.G. Zheng, H. Kubozono, H. Yamada, K. Kato, Y. Ishiwata, C. N. XuTitle：Giant negative thermal expansion in magnetic nanocrystalsAnnouncement information:Nature Nanotechnology Vol: 3 Issue: 12 Page: 724-726Keyword：negative thermal expansion, magnetic nanocrystalAn abstract：Most solids expand when they are heated but a property known as negative thermal expansion (NTE) has been observed in a number of materials, including the oxide ZrW2O8 (1) and the framework material ZnxCd1-x(CN)2 (7, 8). This unusual behaviour can be understood in terms of low-energy phonons (1,2,3,6,7,8), while the colossal values of both positive and negative thermal expansion recently observed in another framework material, Ag3[Co(CN)6], has been explained in terms of the geometric flexibility of its metal-cyanide-metal linkages (9). Thermal expansion can also be stopped in some magnetic transition metal alloys below their magnetic ordering temperature, a phenomenon known as the Invar effect (4,5), and the possibility of exploiting materials with tunable positive or negative thermal expansion in industrial applications has led to intense interest in both the Invar effect and NTE. Here we report the results of thermal expansion experiments on three magnetic nanocrystals – CuO, MnF2 and NiO – and find evidence for NTE in both CuO and MnF2 below their magnetic transition temperatures, but not in NiO. Larger particles of CuO and MnF2 also show prominent magnetostriction (that is, they change shape in response to an applied magnetic field), which results in significantly reduced thermal expansion below their magnetic ordering temperatures [QUERY – are the magnetic ordering temperature and the magnetic transition temperature the same?], whereas this behaviour is not observed in NiO. We propose that the NTE effect in CuO (which is four times larger than that observed in ZrW2O8) and MnF2 is a general property of nanoparticles in which there is strong coupling between [QUERY - please explain magnetolattice coupling in simple terms].