Effects of substituting small amounts of Si for Co on the structure and magnetic properties of Gd_(2)Co_(17) compounds were studied by means of x-ray diffraction and magnetization measurements.All samples are of singl...Effects of substituting small amounts of Si for Co on the structure and magnetic properties of Gd_(2)Co_(17) compounds were studied by means of x-ray diffraction and magnetization measurements.All samples are of single phase with the rhombohedra1 Th_(2)Zn_(17),type structure.The substitution of Si for Co leads to an approximately linear decrease in the unit cell volume.The saturation moment at 1.5 K decreases linearly with increasing Si concentration,being an approximately linear rate of about 4.1μB per substituted Si.The Curie temperature of Gd_(2)Co_(17-x)Si_(x) is found to decrease monotonously from 1213 to 651 K,as x increases from 0 to 3.X-ray diffraction measurements on magnetically aligned powders show that the easy magnetization direction of Gd_(2)Co_(17-x)Si_(x) compounds changes from basal plane to c-axis with increasing Si concentcation.The samples with x=2,3 exhibit a room temperature uniaxial anisotropy.展开更多
The phase composition of melt-spun Nd-Fe-B with intermediate and high Nd concentrations has been studied by Mössbauer effect.Based on the knowledge of the ^(57)Fe hyperfine parameters for Nd_(2)Fe_(14)B,Nd_(2)Fe_...The phase composition of melt-spun Nd-Fe-B with intermediate and high Nd concentrations has been studied by Mössbauer effect.Based on the knowledge of the ^(57)Fe hyperfine parameters for Nd_(2)Fe_(14)B,Nd_(2)Fe_(23)B_(3),and Nd_(1.1)Fe_(4)B_(4),the phases produced during annealing Nd-Fe-B amorphous alloys can be identified.It is found that the Nd_(x)Fe_(81.5-x)B_(18.5) samples with 7≤x≤9 contain the Nd_(2)Fe_(23)B_(3) metastable phase and the Nd1.1Fe4B4 paramagnetic phase.The body-centered-cubic structure of Nd_(2)Fe_(23)B_(3) cannot generate the hard magnetic properties.The samples with 12≤x≤15 consist of the Nd_(2)Fe_(14)B hard magnetic phase and the Nd1.1Fe4B4 paramagnetic phase.The large coercivity for the high Nd content Nd-Fe-B originates from the very fine size of Nd_(2)Fe_(14)B grains below the particle size of the single domain,which may contribute to a pinning effect of domain wall.展开更多
The crystallographic and magnetic structures of Er2Fe15Al2 and Er2Fe12Al5 have been refined in Gaussian peak-shape by Rietveld analysis of Neutron diffrac- tion data. The refined results indicated that Er2Fe15Al2 comp...The crystallographic and magnetic structures of Er2Fe15Al2 and Er2Fe12Al5 have been refined in Gaussian peak-shape by Rietveld analysis of Neutron diffrac- tion data. The refined results indicated that Er2Fe15Al2 compound has Th2Ni17-type hexagonal structure （space group: P63/mmc） and Er2Fe12Al5 has Th2Zn17-type rhom- bohedral structure （space group:R 3m）. The Al atoms prefer 12j and 12k sites with occupancies 0.21 and 0.13, respectively, in Er2Fe15Al2 and prefer 18f, 18h and 6c sites with occupancies 0.35, 0.36 and 0.37, respectively, in Er2Fe12Al5. The magnetic mo- ments of all Fe atoms display ferromagnetically arrangement and the moments of Er atoms couple ferrimagnetically to the moments of the Fe atoms. The moments lie in the plane perpendicular to the six-fold axis and exhibit planar magnetic anisotropy in both samples. The values of To were given and the neutron refined results coincide with that of the magnetic measurements. The relation between magnetic properties and structures was discussed.展开更多
基金Supported by the National Natural Science Foundation of China under Grant No.59525101。
文摘Effects of substituting small amounts of Si for Co on the structure and magnetic properties of Gd_(2)Co_(17) compounds were studied by means of x-ray diffraction and magnetization measurements.All samples are of single phase with the rhombohedra1 Th_(2)Zn_(17),type structure.The substitution of Si for Co leads to an approximately linear decrease in the unit cell volume.The saturation moment at 1.5 K decreases linearly with increasing Si concentration,being an approximately linear rate of about 4.1μB per substituted Si.The Curie temperature of Gd_(2)Co_(17-x)Si_(x) is found to decrease monotonously from 1213 to 651 K,as x increases from 0 to 3.X-ray diffraction measurements on magnetically aligned powders show that the easy magnetization direction of Gd_(2)Co_(17-x)Si_(x) compounds changes from basal plane to c-axis with increasing Si concentcation.The samples with x=2,3 exhibit a room temperature uniaxial anisotropy.
基金Supported by the National Natural Science Foundation of China under Grant No.59525101.
文摘The phase composition of melt-spun Nd-Fe-B with intermediate and high Nd concentrations has been studied by Mössbauer effect.Based on the knowledge of the ^(57)Fe hyperfine parameters for Nd_(2)Fe_(14)B,Nd_(2)Fe_(23)B_(3),and Nd_(1.1)Fe_(4)B_(4),the phases produced during annealing Nd-Fe-B amorphous alloys can be identified.It is found that the Nd_(x)Fe_(81.5-x)B_(18.5) samples with 7≤x≤9 contain the Nd_(2)Fe_(23)B_(3) metastable phase and the Nd1.1Fe4B4 paramagnetic phase.The body-centered-cubic structure of Nd_(2)Fe_(23)B_(3) cannot generate the hard magnetic properties.The samples with 12≤x≤15 consist of the Nd_(2)Fe_(14)B hard magnetic phase and the Nd1.1Fe4B4 paramagnetic phase.The large coercivity for the high Nd content Nd-Fe-B originates from the very fine size of Nd_(2)Fe_(14)B grains below the particle size of the single domain,which may contribute to a pinning effect of domain wall.
基金Nuclear Industry Science Foundation !(H7196B0109) National Nature Science Foun dation of China (19835050)
文摘The crystallographic and magnetic structures of Er2Fe15Al2 and Er2Fe12Al5 have been refined in Gaussian peak-shape by Rietveld analysis of Neutron diffrac- tion data. The refined results indicated that Er2Fe15Al2 compound has Th2Ni17-type hexagonal structure （space group: P63/mmc） and Er2Fe12Al5 has Th2Zn17-type rhom- bohedral structure （space group:R 3m）. The Al atoms prefer 12j and 12k sites with occupancies 0.21 and 0.13, respectively, in Er2Fe15Al2 and prefer 18f, 18h and 6c sites with occupancies 0.35, 0.36 and 0.37, respectively, in Er2Fe12Al5. The magnetic mo- ments of all Fe atoms display ferromagnetically arrangement and the moments of Er atoms couple ferrimagnetically to the moments of the Fe atoms. The moments lie in the plane perpendicular to the six-fold axis and exhibit planar magnetic anisotropy in both samples. The values of To were given and the neutron refined results coincide with that of the magnetic measurements. The relation between magnetic properties and structures was discussed.
