Journal of Applied Physics
Y2Fe14B0.5C0.5 has the same tetragonal structure as Y2Fe14B with space group P4(2)/mnm. Magnetic properties of the Y2Fe14B0.5C0.5 compound have been studied using an extraction magnetometer with a maximum field of 6 T, in the temperature range from 1.5 to 300 K. By means of fitting the hard magnetization curves, the magnetocrystalline anisotropy constants K1, K2, and K3 were determined. It was found that although the magnetocrystalline anisotropy field (mu-0H-a) increases abnormally with increasing temperature as in the case of Y2Fe14B, the dependence of anisotropy constants on temperature is quite different from that of Y2Fe14B. K1 and K3 decrease slightly with increasing temperature. K2 increases abnormally with increasing temperature, which contributes to the abnormal dependence of anisotropy field on temperature. In addition, the substitution of carbon for boron leads to a reduction of 3d-3d interaction and spontaneous magnetization. In contrast, uniaxial anisotropy is increased by the addition of carbon below room temperature.
关键词:
alloys
Journal of Physics D-Applied Physics
Magnetic, electronic transport and magneto-transport behaviours of (Co1-xMnx)(2)P (0.55 <= x <= 0.675) compounds have been systematically investigated. A typical metallic-conductivity behaviour is observed in the ferromagnetic compound (Co0.45Mn0.55)(2)P. The increase in the Mn concentration gives rise to dramatic changes in magnetic, electronic transport and magneto-transport behaviours. With increasing temperature, a first-order phase transition from antiferromagnetism to ferromagnetism takes place at about 145 K, 185K and 240K for x = 0.60, 0.625 and 0.65, respectively. (Co0.4Mn0.6)(2)P and (Co0.375Mn0.625)(2)P compounds experience a metal-insulator transition (Anderson transition) with decreasing temperature. An external magnetic field of 5 T strongly influences the Anderson transition, lowering the transition temperature from 80 to 55K for (Co0.4Mn0.6)(2)P and from 115 to 70K for (Co0.375Mn0.625)(2)P. In contrast with this metal-insulator transition, an insulating behaviour appears in the temperature range from 10 to 300K for (Co0.35Mn0.65)(2)P and (Co0.325Mn0.675)(2)P compounds. Below the antiferromagnetic-ferromagnetic transition temperature TAF-F, a metamagnetic transition can be induced by an external magnetic field. The metamagnetic transition is accompanied by a maximum magnetoresistance ratio of -7%, -6.3% or -3.7% at 5 T in the (Co0.4Mn0.6)(2)P, (Co0.375Mn0.625)(2)P or (Co0.35Mn0.65)(2)P compound at 10 K. The mechanisms of magnetoresistive behaviours are discussed in terms of the formation of a super-zone gap in the antiferromagnetic state.
关键词:
metamagnetic-transition;solid solutions;resistivity;systems;magnetoresistance;anomalies;alloys;field
Materials Science and Engineering a-Structural Materials Properties Microstructure and Processing
A new type of tungsten inert gas (TIG) welding has been developed, in which an ultra-deep penetration is obtained. In order to control the Marangoni convection induced by the surface tension gradient on the molten pool, He gas containing a small amount of oxidizing gas was used. The effect of the concentration Of O-2 and CO2 in the shielding gas on the weld shape was studied for the bead-on-plate TIG welding of SUS304 stainless under He-O-2 and He-CO2 mixed shielding gases. Because oxygen is a surface active element for stainless steel, the addition of oxygen to the molten pool can control the Marangoni convection from the outward to inward direction on the liquid pool surface. When the oxygen content in the liquid pool is over a critical value, around 70ppm, the weld shape suddenly changes from a wide shallow shape to a deep narrow shape due to the change in the direction of the Marangoni convection. Also, for He-based shielding gas, a high welding current will strengthen both the inward Marangoni convection on the pool surface and the inward electromagnetic convection in the liquid pool. Accordingly, at a welding speed of 0.75 mm/s, the welding current of 160 A and the electrode gap of I mm under the He-0.4%O-2 shielding, the depth/width ratio reaches 1.8, which is much larger for Ar-O-2 shielding gas (0.7). The effects of the welding parameters, such as welding speed and welding current were also systematically investigated. In addition. a double shielding gas method has been developed to prevent any consumption of the tungsten electrode. (c) 2008 Elsevier B.V. All rights reserved.
关键词:
Weld shape;Oxygen;Helium;Marangoni convection;Electromagnetic;convection;Double shielding gas;gas tungsten arc;shape variations;oxide fluxes;penetration;parameters
Journal of Materials Research
The morphology of the dark and bright regions observed by transmission electron microscopy for the Zr(64.13)Cu(15.75)Ni(10.12)Al(10) bulk metallic glass strongly depends on the ion beam parameters used for ion milling. This indicates that the ion beam could introduce surface fluctuation to metallic glasses during ion milling.
关键词:
room-temperature
Physica B-Condensed Matter
The magnetic properties and magnetocaloric effect of Tb(1-x)Y(x)CoC(2) (x = 0, 0.1, 0.2, 0.3, 0.4) compounds have been investigated systematically. All the compounds undergo second-order transitions from paramagnetic to ferromagnetic states without thermal and magnetic hysteresis. With increasing Y content from 0 to 0.4, the Curie temperatures decrease nearly linearly from 28 to 18 K. The nature of the second-order phase transitions can be confirmed by Arrott plots. For Tb(0.6)Y(0.4)CoC(2) compound, the maximum value of the magnetic entropy change -Delta S(M) at 20 K is 9.35 J kg(-1) K(-1) for an external field change of 5T (5.14 J kg(-1) K(-1) for 2T). The large reversible magnetic entropy change makes Tb(0.6)Y(04)CoC(2) compound an attractive candidate for the application at hydrogen liquefaction temperature. (C) 2010 Elsevier B.V. All rights reserved.
关键词:
Curie temperature;Magnetocaloric effect;Magnetic properties;ac susceptibility
Powder Diffraction
K(2)Zn(3)(P(2)O(7))(2) was synthesized by solid state reaction and its crystal structure was determined by ab initio method from powder X-ray diffraction (XRD) data. The title compound was determined to be orthorhombic with space group P2(1)2(1)2(1), Z=4, and lattice parameters a=12.901(8) angstrom, b=10.102(6) angstrom, and c=9.958(1) angstrom. Values of lattice parameters from 303 to 573 K were measured by temperature-dependent XRD. Thermal expansion coefficients alpha(0), lattice parameters, and cell volume at 0 K were determined to be alpha(0)(a)=1.62327X 10(-4)/K, a(0)=12.855(4) angstrom, alpha(0)(b) = 1.17921 X 10(-4)/K, b(0)=10.070(8) angstrom, alpha(0)(c)=2.62364X 10(-4)/K, c(0)=9.880(4) angstrom, and alpha(0)(V) = 6.599 X 10(-2) /K, V(0) = 1278.967(0) angstrom(3). The specific heat equation as a function of temperature was determined to be C(p)=0.77115 +0.00231 T-1241.60027T(-2)- 1.4133 X 10(-6)T(2) (J/K g), for temperatures from 198 to 710 K. The melting point estimated from the mu-DTA heating curve is 795 degrees C. (C) 2008 International Centre for Diffraction Data. [DOI: 10.1154/1.2992517]
关键词:
K(2)Zn(3)(P(2)O(7))(2);structure determination;thermal expansion;coefficient;specific heat;powder-diffraction;refinement;zno
Ieee Transactions on Magnetics
The spin orientation and spontaneous magnetostriction of multicomponent TbxDy1-x-yPry(Fe0.9B0.1)(1.93) (0.10 less than or equal to x less than or equal to 0.25, 0.30 less than or equal to y less than or equal to 0.60) Laves phases were studied by step-scanning their (440) X-ray diffraction lines. The easy magnetization direction (EMD) of the Laves phases changed from the (100) to (111) axis when x was increased from 0.10 to 0.25. With increasing y, the EMD of Tb0.15Dy0.85-yPry(Fe0.9B0.1)(1.93) and Tb0.2Dy0.8-yPry(Fe0.9B0.1)(1.93) Laves phases reoriented from the (100) to (111) axis. The magnetostriction coefficient lambda(111) of TbxDy1-x-yPry(Fe0.9B0.1)(1.93) Laves phases increased with increasing x (or y) when y (or x) was kept constant.
关键词:
Laves phases;magnetostriction;spin orientation;X-ray diffraction;anisotropy compensation;alloys
