S.P. Li
,
S.X. Zhao
,
M.X Pan
,
D.Q. Zhao
,
and X.C.Chen (Institute of Physics
,
Chinese Academy of Sciences
,
Beijing 100080
,
China)
金属学报(英文版)
Dependence of the morphology of α(Al)-Mg2Si eutectic on the solidification velocity, and its orientation characteristics were investigated by thermoanalysis, directional solidification and electron diffraction techniques in this study.The eutectic morphology transformed from lamellae to rods with the increasing of the solidification velocity. Simultaneously, the orientation relationship changed from (100)Mg2Si/(100)Al;[110]Mg2si/[110]al to (011)Mg2si/(121)Al;[111]Mg2Si/[111]Al and (010)Mg2Si/(110)Al; [100]Mg2Si/[111]Al. Transformation of the eutectic morphology was related to the change of the preferred orientation of phase Mg2si.
关键词:
:α(Al)-Mg_2Si eutectic
,
null
,
null
Journal of Applied Physics
The effect of Co substitution on structure, phase transformation, and magnetic properties of R(16)Fe(76-x)Co(x)C(8) (R equivalent to Nd, Dy; 0 <= x <= 76) alloys prepared by a remilling process has been studied systematically. The process of remilling and subsequent annealing is more beneficial for the formation of Nd(2)(Fe,Co)(14)C compound in Nd(16)Fe(76-x)Co(x)C(8) alloys than in Dy(16)Fe(76-x)Co(x)C(8) alloys. The R(2)(Fe,Co)(14)C phase is obtained for Nd(16)Fe(76-x)Co(x)C(8) alloys with 0 <= x <= 20 and Dy(16)Fe(76-x)Co(x)C(8) alloys with 0 <= x <= 25. Higher Co content results in the formation of Nd(2)(Fe,Co)(17)C(delta)-type phase and Dy(Fe,Co)(7) phase for Nd(16)Fe(76-x)Co(x)C(8) and Dy(16)Fe(76-x)Co(x)C(8) alloys, respectively. The high coercivity, (i)H(c)=48.5 kOe, is achieved for Dy(16)Fe(51)Co(25)C(8) alloy. (C) 2008 American Institute of Physics.
关键词:
permanent-magnets;r2fe14c;carbides;carbon
Applied Physics Letters
We report the band-structure changes near Fermi level for single-walled carbon nanotubes (SWNTs) with diameters down to 1 nm from the study of soft-x-ray absorption and resonant emission spectroscopy. The observed quantum confinement of SWNTs affects both pi and sigma bands and bandgap through the rehybridization of pi and sigma orbitals. The significant changes of electronic structure are proved to be a measure for the mean diameter of the macroscopic amounts of SWNTs. (C) 2008 American Institute of Physics.
关键词:
electronic-structure;absorption;graphite;fluorescence;scattering
Applied Physics Letters
A series of polycrystalline Ca(3)Co(2-x)Mn(x)O(6) with 0.93 < x < 1.07 are prepared in order to investigate the effect of Co:Mn ratio around x similar to 1.0 on the multiferroicity. It is found that the ferroelectric polarization P at low temperature shows significant dependence on the Co:Mn ratio, forming a V-shaped pattern with the lowest point at x similar to 0.99. It is proposed that the suppression of P with the Co:Mn ratio approaching to the best Co/Mn order originates from the disruption of the long range spin order. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3464289]
关键词:
calcium compounds;ferroelectric materials;multiferroics;one-dimensional oxides;ca3co1+xmn1-xo6
Journal of Applied Physics
A series of orthorhombic manganites Gd(1-x)Ho(x)MnO(3) (0 <= x <= 0.5) are synthesized. The Ho doping leads to a transition of paraelectric phase into ferroelectric one, making Gd(1-x)Ho(x)MnO(3) multiferroic. It is argued that the enhanced electric polarization originates from the transition of the A-type Mn(3+) anti-ferromagnetic state into the spiral spin order driven by the reduction of Mn-O-Mn bond angle due to the doping. The noncollinear spin order of the A-site Ho(3+) spins at high doping level may also make contribution to the polarization. (c) 2011 American Institute of Physics. [doi: 10.1063/1.3535543]
关键词:
polarization;perovskite
Applied Physics Letters
Using the density functional calculations, we investigated the effect of nanoprecipitation on the magnetostriction of Fe(1-x)Ga(x) alloys. While the B2-like FeGa clusters undergo slight tetragonal distortion, D0(3)-like FeGa clusters remain cubic in the Fe matrix. Moreover, we found that B2-like nanostructures produce negative magnetostriction, whereas D0(3)-like nanostructures give small positive magnetostriction in the hypothetical inhomogeneous structures. Therefore, the formation of nanoscale precipitates cannot be the reason for the extraordinary enhancement of magnetostriction of Fe(1-x)Ga(x) alloys. (C) 2010 American Institute of Physics. [doi:10.1063/1.3533659]
关键词:
augmented-wave method;fe-ga alloys;al alloys;magnetoelasticity
Applied Physics Letters
The effect of nonmagnetic Y partial substitution at the Dy site in Dy(1-x)Y(x)MnO(3) up to x=0.2 on magnetism, specific heat, and ferroelectricity is investigated, which resulted in a preliminary multiferroic phase diagram. It is revealed that the Y partial substitution suppresses the Dy-spin ordering point (T(Dy)) and ferroelectric ordering point (T(FE)) but enhances the Mn-spin ordering point (T(N)). The interaction between the spins of Dy and Mn is remarkably affected by Y substitution. The measured electrical polarization depends on the Y substitution in a complex way because the ferroelectricity is sensitive to the interaction between the spins of Dy and Mn. (c) 2011 American Institute of Physics. [doi: 10.1063/1.3536506]
关键词:
ferroelectricity;polarization
Journal of Applied Physics
The effects of B and C substitution for Sn on phase components, Curie temperature T-C, and magnetocaloric effect of melt-spun Mn3Sn2-xMx (M = B, C; x = 0-0.5) ribbons have been investigated. X-ray diffraction (XRD) results show that the main phase in the as-spun Mn3Sn2-xMx (M = B, C; x = 0-0.5) ribbons is Mn3Sn2 of Ni3Sn2-type (Pnma). Minor Mn2B (when x >= 0.1) or Mn5C2 (when x > 0.1) secondary phase is formed, and their amounts increase with increasing B and C concentration, respectively. The Curie temperature T-C of these ribbons varies in the temperature range of 240-250K. The peak values of the maximal magnetic entropy change, -Delta S-M(max), are about 13.6-18.3 mJ/cm(3) K for B-substituted ribbons and 13.6-17.5 mJ/cm(3) K for C-substituted ribbons, respectively, at a maximum applied field of 50 kOe. These values are about one fifth that of Gd (81.4 mJ/cm(3) K). However, the relatively broader temperature range of the half maximum of Delta S-M peak (similar to 100K), low-cost and nontoxic elements still make Mn3Sn2-based ribbons the promising candidates for magnetic refrigeration applications close to room temperature. (C) 2012 American Institute of Physics. [doi:10.1063/1.3671789]
关键词:
room-temperature
Applied Physics Letters
Martensitic transformation in Ni(2+x)Mn(1-x)Ga alloys is known to be controlled by the soft tetragonal elastic constant C' of the high-temperature austenitic phase. The temperature (T) and composition (x) dependence of C'(T, x) are calculated using the first-principles exact muffin-tin orbitals method. We show that the temperature factor of C' is dominated by the phonon-smearing term. The competition between the negative alloying effect (partial derivative C'/partial derivative x < 0) and the positive temperature effect (partial derivative C'/partial derivative T > 0) is found to lead to nearly constant C'(T(M)(x), x) at the critical temperature TM(x). We demonstrate that a proper account of the temperature and composition dependence of C'(T, x) is indispensable for reasonable theoretical TM(x) values. VC 2011 American Institute of Physics. [doi: 10.1063/1.3603935]
关键词:
phase
