Jing-yun Wang

Structure and magnetic properties of Pr2Fe17-xMnx (x=0-9) compounds

The influence of Mn substitution for Fe on the structure and magnetic properties of Pr2Fe17−xMnx compounds with 0⩽x⩽9 was investigated. X-ray diffraction indicates that all samples are single phase with the rhombohedral Th2Zn17-type structure. The unit cell volume V remains nearly constant with increasing manganese content up to x=2, then increases linearly at a rate of about 2.5 A3 per Mn atom up to x=8 and there is a large increase of cell volume at x=9. The Curie temperature increases a little from 298 K at x=0 to 308 K at x=1, and then decreases to 37 K at x=9 quickly. The saturation magnetization at 5 K was found to decrease monotonously with increasing Mn concentration. The thermal magnetization curves M(T) of the compounds with x=1–9 show a strong decrease below TC with decreasing temperature. Also it presents considerable magnetic hardness at low temperature. This can be attributed to the presence of narrow Bloch walls.

Structure and magnetic properties of SM2Fe17-xMnx compounds

The effect of Mn substitution for Fe in Sm2 Fe17-x Mnx compounds on the structure and magnetocrystalline anisotropy was studied by x-ray diffraction and magnetization measurements. The compounds prepared have a rhombohedral Th2 Zn17 -type structure single phase except for a small amount of -Fe for x = 1-4, while x = 5 has Nd3 (Fe,Ti)29 -type monoclinic structure. The Curie temperature TC is found to increase to 430 K for x = 1, then decrease to 255 K for x = 5. The saturation magnetization at 5 K decreases with increasing Mn concentration. Room temperature anisotropy changes from easy planar type to cone type and to easy c -axis type with increasing Mn concentration for x = 1, 2 and 3 respectively. The anisotropy field for x = 3 is about 1 T at 100 K and decreases to 0.4 T at room temperature.

Structure and magnetic properties of Pr2Co17−xMnx compounds

The structure and magnetic properties of Pr2Co17−xMnx (x=0–14) compounds were studied. A single phase with the rhombohedral Th2Zn17-type structure was obtained from x-ray diffraction patterns for x=0–11. The unit-cell volumes were found to increase linearly at a rate of about 5.7 A3 per Mn atom. Both the Curie temperature and saturation magnetic moment at 5 K decrease monotonously with increasing Mn concentration. The spin reorientation was found in Pr2Co17−xMnx compounds for x=1–5. The magnetic phase diagram of the compounds was given. A transition from ferromagnetic to antiferromagnetic for x=8–9 was observed due to the Mn substitution. At high Mn concentration (x=12,13,14), a rare-earth intermetallic 3:29 phase was found. This kind of 3:29 phase shows a paramagnetic character when the temperature is above 5 K.

Magnetic properties of (La1−xPrx)6Fe11Al3 compounds

The synthesis, structure and magnetic properties of (La1-xPrx)(6)Fe11Al3 (x = 0.0-1.0) compounds are investigated in this work. Upon substitution of Pr for La, the unit-cell volume decreases linearly with the Pr content, but the long-range magnetic-ordering temperature rises. A first-order magnetic process is observed at 5 K, which becomes more evident with increasing Pr concentration while the Pr concentration has little effect on the value of the critical field of the transition. With increasing temperature, the magnetic state of the compounds changes from antiferromagnetic to spin cluster, and finally to the paramagnetic state

Structure and magnetic properties of Tb2Co17-xMnx compounds

X-ray diffraction (XRD) and magnetization measurements were employed to investigate the effects of Mn substitution for Co on the structure and magnetic properties of Tb2Co17−xMnx compounds with x=0–7. XRD patterns show that all samples are single phase except the samples with x=6 and 7 which contain a small amount of impurity. The substitution of Mn for Co leads to a monotonic increase in unit cell volume. The saturation magnetization at 5 K remains nearly unchanged upon Mn substitution, while the Curie temperature decreases monotonically. XRD measurements on magnetically aligned powders with x=0–7 exhibit an easy-plane type of magnetic anisotropy at room temperature. For x=2, 3, and 4, spin reorientation transitions above room temperature are observed in the M–T curves. The magnetic phase diagram is given.

Fe-Fe bond length and exchange interaction in Y2Fe17-xGax (x = 0-8) compounds

The Ga-occupancy factors and the Fe-Fe bond lengths resulting from the Rietveld refinement of X-ray diffraction data show a critical point at a Ga content between x = 5 and 6. The Fe-Fe exchange-interaction constant J(FeFe) derived from the Curie temperature increases linearly with increasing Ga concentration when x less than or equal to 4, remains almost unchanged for x = 4-6, then increases sharply when x > 6. The variation of the Fe-Fe exchange-interaction constant may be qualitatively explained by the variation of the Ga preferential occupancy aad the Fe-Fe bond lengths

Structure and magnetic properties of (Nd1−xCex)6Fe13Al compounds

Samples of (Nd1−xCex)6Fe13Al (x=0.1, 0.2, 0.3, 0.4, 0.5, 0.6) were prepared by arc melting and annealed for 2 weeks at 700 °C. The x-ray diffraction patterns for the (Nd1−xCex)6Fe13Al samples show that all the above-mentioned samples crystallize with the Nd6Fe13Si-type tetragonal phase. The unit-cell volume v increases first and then decreases as the Ce content increases. The Curie temperature and the spontaneous magnetization decrease almost linearly with increasing Ce concentration. All these prove the existence of the mixed valence of Ce3+ and Ce4+. A complicated temperature dependence of magnetization is observed. Although the series is ferromagnetic at high temperature, there is a low-temperature peak in each M–T curve, which is in agreement with spin-glass behavior. This phenomena is reported in 6:13:1-type compounds.

Magnetic properties of R2Co15Al2 compounds with R=Y, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, and Tm

An investigation of the structure and the magnetic anisotropy of R2Co15Al2 (R=Y, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, and Tm) compounds has been performed by means of x-ray diffraction and magnetization measurements. X-ray diffraction shows the prepared compounds to be single phase, having the hexagonal Th2Ni17-type structure for R=Y, Ho, Er, and Tm and the rhombohedral Th2Zn17-type structure for R=Ce, Pr, Nd, Gd, Tb, and Dy. Except for the Ce compound, the unit-cell volumes of R2Co15Al2 compounds decrease in accordance with the lanthanide contraction. Substitution of Al for Co in R2Co17 leads to a decrease of the saturation magnetization at 1.5 K and Curie temperature. The exchange-coupling constants JCo–Co and JR–Co have been calculated by using the method based on magnetic ordering temperature. It is found that the JR–Co has a small dependence on the R elements and is almost not affected by the Al substitution. The Ce compound is found to exhibit an anomalous lattice parameter and magnetic characteristi...

The magnetocrystalline anisotropy of R/sub 2/Co/sub 17-x/Mn/sub x/ (R=Pr, Nd, Tb, Dy and Ho) compounds

The effect of Mn substitution on the magnetocrystalline anisotropy of R/sub 2/Co/sub 17-x/Mn/sub x/ (R=Pr, Nd, Tb, Ho and Dy) compounds have been investigated by means of X-ray diffraction (XRD) and magnetic measurements, XRD measurement on magnetically aligned samples demonstrates that for Pr (1 3. The magnetic phase diagrams are given. The spin-reorientation transition might be understood as the result of the competition between the magneto-crystalline anisotropy of the R-sublattice and that of the 3d-sublattice. Room-temperature magnetocrystalline anisotropy fields HA firstly increases and then decreases with increasing Mn substitution, attaining the maximum at x=2-3. The enhancement of anisotropy is explained by preferred substitution of Mn atom in 6c Co sites. From the measurement of magnetization curve along and perpendicular to the c-axis at different temperature around the T/sub sr/, it can be implied that the spin-reorientation transitions are a continuous moment reorientation.

Structure, exchange interactions and magnetic anisotropy of Ho2Co17−xSix compounds

The structural and magnetic characteristics of Ho2Co17−xSix (x=0, 0.5, 1.0, 1.5, 2.0, 2.5, and 3.0) compounds have been investigated by means of x-ray diffraction and magnetic measurements. Powder x-ray diffractograms show that all samples are single phase and have the hexagonal Th2Ni17-type or the rhombohedral Th2Zn17-type structure. The substitution of Si for Co leads to a monotonous decrease in unit cell volume v and Curie temperature TC. The compensation points are observed for the samples with x=2.5 and 3.0, and the compensation temperatures shift to higher temperatures with increasing Si content. The intersublattice-molecular-field coefficient, nHo–Co, has been determined on the basis of magnetization curves at the compensation temperature. It has been found that the Si substitution for Co has little influence on Ho–Co exchange interaction. The magnetic phase diagram has been determined from the temperature dependence of magnetization and the XRD patterns of magnetically oriented powder samples. The...