Structure, magnetic properties and magnetostriction of Sm0.9Pr0.1(Fe1-xCox)2 compounds have been investigated by means of X-ray diffraction, a.c. initial susceptibility, extracting sample magnetometer, Mossbauer spec-...Structure, magnetic properties and magnetostriction of Sm0.9Pr0.1(Fe1-xCox)2 compounds have been investigated by means of X-ray diffraction, a.c. initial susceptibility, extracting sample magnetometer, Mossbauer spec-troscopy and standard strain gauge techniques. The lattice parameter a of the MgCu2-type Laves compounds Sm0.9Pr0.1(Fe1-xCox)2 decreases nonlinearly with increasing Co concentration, deviating from the Vegard's law. Curie temperature Tc increases initially from 668 K for x=0 to 694 K for x=0.2 and then decreases to 200 K for x=1.0. The saturation magnetization Ms at temperatures 1.5 K, 77 K and 300 K have the same variation tendency as the composition dependence of Curie temperature, in consistence with rigid-band model. The easy magnetization direction (EMD) of Sm0.9Pr0.1(Fe1-xCox)2 lies along [111] direction in the range x<0.6, and changes to [110] for x=0.8, while Sm0.9Pr0.1Co2 stays in the paramagnetic state at room temperature. The composition dependence of the average hyperfine field,Hhf , demonstrates a similar variation tendency as that of the saturation magnetization Ms and Curie temperature Tc. The spontaneous magnetostricton Am increases with increasing Co content. The saturation magnetostriction λs decreases monotonically with increasing x, which is caused by the increase of magnetostriction constant λ100 with opposite sign to that of Am. A two-sublattice model has been proposed to understand the intermediate region between the [111] and [110] spin configurations, which can also be used to explain the temperature dependence of magnetization.展开更多
Sinee Coey et al. prepared the R<sub>2</sub>Fe<sub>17</sub>N<sub>x</sub> compounds by means of doping the nitrogenin gas-phase reaction, the magnetic properties of R<sub>2<...Sinee Coey et al. prepared the R<sub>2</sub>Fe<sub>17</sub>N<sub>x</sub> compounds by means of doping the nitrogenin gas-phase reaction, the magnetic properties of R<sub>2</sub>Fe<sub>17</sub> intermetallic compounds havebeen significantly improved. This aroused wide interest of relevant scientists. Recent re-search results show that Sm<sub>2</sub>Fe<sub>17</sub>N<sub>x</sub> has excellent intrinsic magnetic properties, but the nitridesR<sub>2</sub>Fe<sub>17</sub>N<sub>x</sub> consisting of other rare-earth elements except Sm, have an easy-plane anisotropy.In addition, Sm is very expensive. This kind of permanent magnetic materials is展开更多
Polycrystalline Pr2Fe17-xMnx（x = 0, 1, and 2）alloys were studied by X-ray diffraction（XRD）, heat capacity, ac susceptibility, and isothermal magnetization measurements. All the alloys adopt the rhombohedral Th2Zn1...Polycrystalline Pr2Fe17-xMnx（x = 0, 1, and 2）alloys were studied by X-ray diffraction（XRD）, heat capacity, ac susceptibility, and isothermal magnetization measurements. All the alloys adopt the rhombohedral Th2Zn17-type structure. The Curie temperature increases from 283 K at x = 0 to 294 K at x = 1, and then decreases to 285 K at x = 2. The magnetic phase transition at the Curie temperature is a typical second-order paramagnetic–ferromagnetic transition. For an applied field change from0 to 5 T, the maximum-△SM for Pr2Fe17-xMnxalloys with x = 0, 1, and 2 are 5.66, 5.07, and 4.31 J·kg^-1·K^-1,respectively. The refrigerant capacity（RC） values range from 458 to 364 J·kg^-1, which is about 70 %–89 % that of Gd. The large, near room temperature △SM and RC values,chemical stability, and a high performance-to-cost ratio make Pr2Fe17-xMnxalloys be selectable materials for room temperature magnetic refrigeration applications.展开更多
基金This work has been supported by the projects No.59725103 and 59871054 of the National Natural Sciences Foundation of China and by the Science and Technology Commnission of Shenyang and Liaoning.Z.J.Guo as aiso indebted to Prof.A.S.Miarkosyan(Russia)for helpful discussions.
文摘Structure, magnetic properties and magnetostriction of Sm0.9Pr0.1(Fe1-xCox)2 compounds have been investigated by means of X-ray diffraction, a.c. initial susceptibility, extracting sample magnetometer, Mossbauer spec-troscopy and standard strain gauge techniques. The lattice parameter a of the MgCu2-type Laves compounds Sm0.9Pr0.1(Fe1-xCox)2 decreases nonlinearly with increasing Co concentration, deviating from the Vegard's law. Curie temperature Tc increases initially from 668 K for x=0 to 694 K for x=0.2 and then decreases to 200 K for x=1.0. The saturation magnetization Ms at temperatures 1.5 K, 77 K and 300 K have the same variation tendency as the composition dependence of Curie temperature, in consistence with rigid-band model. The easy magnetization direction (EMD) of Sm0.9Pr0.1(Fe1-xCox)2 lies along [111] direction in the range x<0.6, and changes to [110] for x=0.8, while Sm0.9Pr0.1Co2 stays in the paramagnetic state at room temperature. The composition dependence of the average hyperfine field,Hhf , demonstrates a similar variation tendency as that of the saturation magnetization Ms and Curie temperature Tc. The spontaneous magnetostricton Am increases with increasing Co content. The saturation magnetostriction λs decreases monotonically with increasing x, which is caused by the increase of magnetostriction constant λ100 with opposite sign to that of Am. A two-sublattice model has been proposed to understand the intermediate region between the [111] and [110] spin configurations, which can also be used to explain the temperature dependence of magnetization.
文摘Sinee Coey et al. prepared the R<sub>2</sub>Fe<sub>17</sub>N<sub>x</sub> compounds by means of doping the nitrogenin gas-phase reaction, the magnetic properties of R<sub>2</sub>Fe<sub>17</sub> intermetallic compounds havebeen significantly improved. This aroused wide interest of relevant scientists. Recent re-search results show that Sm<sub>2</sub>Fe<sub>17</sub>N<sub>x</sub> has excellent intrinsic magnetic properties, but the nitridesR<sub>2</sub>Fe<sub>17</sub>N<sub>x</sub> consisting of other rare-earth elements except Sm, have an easy-plane anisotropy.In addition, Sm is very expensive. This kind of permanent magnetic materials is
基金financially supported by the U.S. Department of Energy by Iowa State University (No. DE-AC0207CH11358)the Guangdong Provincial Science & Technology Program (No. 2010B050300008)+2 种基金the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry (No. x2clB7120290)the Guangzhou Municipal Science and Technology Program (No. 12F582080022)the Fundamental Research Funds for the Central Universities (Nos. 2012ZZ0013 and 2011ZM0014)
文摘Polycrystalline Pr2Fe17-xMnx（x = 0, 1, and 2）alloys were studied by X-ray diffraction（XRD）, heat capacity, ac susceptibility, and isothermal magnetization measurements. All the alloys adopt the rhombohedral Th2Zn17-type structure. The Curie temperature increases from 283 K at x = 0 to 294 K at x = 1, and then decreases to 285 K at x = 2. The magnetic phase transition at the Curie temperature is a typical second-order paramagnetic–ferromagnetic transition. For an applied field change from0 to 5 T, the maximum-△SM for Pr2Fe17-xMnxalloys with x = 0, 1, and 2 are 5.66, 5.07, and 4.31 J·kg^-1·K^-1,respectively. The refrigerant capacity（RC） values range from 458 to 364 J·kg^-1, which is about 70 %–89 % that of Gd. The large, near room temperature △SM and RC values,chemical stability, and a high performance-to-cost ratio make Pr2Fe17-xMnxalloys be selectable materials for room temperature magnetic refrigeration applications.
