On the magnetic properties of the Y1−xGdxCo4B compounds (original) (raw)
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Journal of Magnetism and Magnetic Materials, 2011
The YCo 4 Ge intrinsic magnetic properties; such as the saturation magnetization and the magnetocrystalline anisotropy parameters; are determined at 5, 100, 200 and 300 K from a fit of the isothermal magnetization curves measured in applied field up to 10 T. Ge for Co substitution induces a reduction of the first order anisotropy parameter as well as of the uniaxial anisotropy field. At 4 K an anisotropy field of 5.8 T is obtained, whereas a value of that is observed at room temperature. The magnetocrystalline anisotropy found for YCo 4 Ge is significantly reduced upon heating from 4 to 300 K. The investigation of the magnetic properties of YCo 4 Ge in both the ordered and the paramagnetic phases shows that this YCo 4 Ge compound exhibits a typical itinerant ferromagnetic behavior. The effect of applied pressure on the isothermal magnetization has been investigated showing that the volume has an important influence on the magnetization of YCo 4 Ge. The influence of the Ge for Co substitution on the Co-Co exchange interaction is also discussed. The results are compared and commented on in the light of earlier reports for YCo 5 and other Co containing phases.
Magnetic properties of (GdxY1−x)Co2B2 compounds
Journal of Magnetism and Magnetic Materials, 1993
Magnetic measurements were performed on the (Gd,Yr_,)Co,B, compounds, in the temperature range 2-800 K and fields up to 70 kOe. YCo,B, is a paramagnet. The (Gd,Y,_,jCo,B, compounds with x t 0.2 shows a ferromagnetic type ordering. The saturation magnetization at 2 K coincides only with the contribution of gadolinium. The Curie temperatures are nearly linearly dependent on the composition. Above the Curie points, the thermal variations of the magnetic susceptibility can be described as a superposition of a temperature independent term x0 on a Curie-Weiss behavior. The Curie constants are determined by the contribution of Gd 3+ ions only. The x0 values increase when the gadolinium content is greater. The observed properties are discussed in the wider framework of the magnetic behavior of cobalt in GdCo,B, compounds.
Electronic structure and magnetic properties of the Th Y1−Co4B solid solution
Computational Materials Science, 2010
Detailed theoretical and experimental investigations of the electronic and magnetic properties of the Th x Y 1Àx Co 4 B compounds have been performed. The neutron powder diffraction shows that by Th for Y substitution, Th atoms occupy preferentially one (1a) of the two Y sites (1a and 1b). The preferential occupation on 1a and 1b crystal sites investigated by theoretical calculations is in good agreement with powder neutron diffraction results. The magnetic properties of the Th x Y 1Àx Co 4 B compounds are strongly influenced by the Th content x. The Curie temperature of the compound decreases with Th content from 380 K for YCo 4 B to 303 K for ThCo 4 B. The Th for Y substitution alter the magnetic coupling of the Co 2c atoms, which have the dominant contribution to the magnetization of the system. The magnetic moments behavior in the Th x Y 1Àx Co 4 B compounds is also related to the preferential occupation of crystallographic 1a and 1b sites by Th and Y atoms, respectively. The agreement between the calculated magnetic moments and the corresponding experimental results is discussed. All theoretical investigations of the electronic and magnetic properties of the system have been done using the Korringa-Kohn-Rostoker (KKR) band structure method in the ferromagnetic state. The substitutional disorder in the system has been accounted for by means of Coherent Potential Approximation (CPA).
Structural and Magnetic Investigations of Yb Substituted Y1-xYbxBaCo4O7 (0 ≤ x ≤ 0.5) Compound
Integrated Ferroelectrics, 2019
Structural and magnetic behavior of a series of new cobaltite Y 1-x Yb x BaCo 4 O 7 (0 x 0.5), prepared using the conventional solid state reaction method have been investigated. Increasing Yb content leads to the increase in magnitude of magnetic moment and decreases the ferromagnetic transition (T c) values. It is found that the predominant antiferromagnetic character of exchange interactions between cobalt ions, a ferromagnetic component, seemed to be strong enough to be detected still at room temperature. Our findings show that these materials exhibit ferromagnetic like transition at about T c ¼ 91 K, 80 K, 67 K, 55 K, 51 K and 45 K for composition x ¼ 0.0, 0.1, 0.2, 0.3, 0.4 and 0.5, respectively. We found that these materials exhibit spin-glass like state which dominates at low temperature.
Journal of Physics and Chemistry of Solids, 2008
The crystal and magnetic properties of the Nd 1Àx Gd x Co 4 B compounds for 0pxp1 have been studied by X-ray powder diffraction, magnetization and differential scanning calorimetry (DSC) measurements. These compounds crystallize in a hexagonal CeCo 4 B-type structure with the P6/mmm space group. The substitution of Gd for Nd leads to a decrease of the unit-cell parameter a and the unit-cell volume V, while the unit-cell parameter c remains almost constant. Magnetic measurements indicate that all samples are ordered magnetically below room temperature. The Curie temperatures determined by the DSC technique increase linearly as Nd is substituted by Gd. The saturation magnetization at 5 K decreases upon the Gd substitution up to x ¼ 0.6, and then increases again.
Magnetocaloric effect of the multiphase Gd4−xTbxCo3 system
Philosophical Magazine, 2018
Crystal structure, microstructural chemical analysis, magnetic properties and magnetocaloric effect for 'as cast' and annealed Gd 4−x Tb x Co 3 (x = 0-4) were investigated. Only Gd 4 Co 3 was homogeneous and crystallised in the hexagonal Ho 4 Co 3-type of crystal structure. Samples substituted with terbium proved to be a mixture of (Gd, Tb) 12 Co 7 and (Gd,Tb)Co 2 phases. With the increase of terbium content the entropy change increased and for the samples with x = 3, 4 reached the highest values. Even 'ascast' samples exhibit pronounced values of the magnetocaloric parameters.
The paramagnetic contribution in the magnetization behavior of Y 1− x Gd x Ba 2Cu 3O 7
Physica B-condensed Matter, 2002
Polycrystalline samples of Y 1Àx Gd x Ba 2 Cu 3 O 7 with different Gd contents (x ¼ 1; 0:75; 0:5; 0:25) were prepared using the usual solid state reaction method. X-ray characterization of these samples showed an orthorhombic phase. The lattice parameters a; b; and c were found to increase with increasing Gd concentration which is due to the larger volume of Gd atoms. Magnetization and transport measurements show the same transition temperature of 91 K for all samples studied. Initial and magnetization hysteresis loop measurements showed that the paramagnetic behavior is dominant at high fields. r
Magnetic Properties and the Electronic Structure of the Gd0.4Tb0.6Co2 Compound
Materials
We report on the comprehensive experimental and theoretical studies of magnetic and electronic structural properties of the Gd0.4Tb0.6Co2 compound crystallization in the cubic Laves phase (C15). We present new results and compare them to those reported earlier. The magnetic study was completed with electronic structure investigations. Based on magnetic isotherms, magnetic entropy change (ΔSM) was determined for many values of the magnetic field change (Δμ0H), which varied from 0.1 to 7 T. In each case, the ΔSM had a maximum around room temperature. The analysis of Arrott plots supplemented by a study of temperature dependency of Landau coefficients revealed that the compound undergoes a magnetic phase transition of the second type. From the M(T) dependency, the exchange integrals between rare-earth R-R (JRR), R-Co (JRCo), and Co-Co (JCoCo) atoms were evaluated within the mean-field theory approach. The electronic structure was determined using the X-ray photoelectron spectroscopy (X...
Magnetic phase transitions in Gd3Co
Journal of Alloys and Compounds, 1993
Magnetization, electrical resistivity, thermal expansion, magnetostriction and sound velocity were measured for Gd3Co single crystals. The compound has an orthorhombic Fe3C-type crystal structure and exhibits an antiferromagnetic arrangement of Gd magnetic moments below TN = 131 K. First-order phase transitions from the antiferromagnetic to the forced ferromagnetic state are observed along the b and c axes at a critical field He--0.8 T. Along the a axis, Gd3Co also becomes a forced ferromagnet at approximately 1.5 T, but the magnetization process occurs by the rotation of Gd magnetic moments. An antiferromagnetic ordering of the Co sublattice appears below T* =3.7 K. Anisotropy of the electrical resistivity is found below TN. The field-induced antiferromagnetic to ferromagnetic transitions are accompanied by large magnetoresistance (Ap/po= --50%) and magnetostriction (A//l--3.8×10 -4) as well as by a large change of the sound velocity of the shear wave in the bc plane (from 675 m s-i down to 220 m s-~). Magnetic phase diagrams of Gd3Co are given for different directions of the applied field.
The electronic and magnetic properties of YbxGd1-xNi5 systems
Acta Physica Polonica Series a
The intermetallic compounds YbxGd1-xNi5 crystallize in the hexagonal CaCu5-type structure. Based on wide ranging SQUID-type magnetometer, it was shown that the saturation magnetization decreases with growing concentration of ytterbium. The opposite tendency was observed for the Sommerfeld coefficient obtained in the heat capacity measurements. These results are confirmed using ab initio band structure calculations.