The spontaneous magnetic transitions and corresponding magnetoelastic properties of intermetallic compounds RMn2Ge2（R=Gd, Tb and Dy） were investigated by using the X-ray diffraction method and magnetic measurement. ...The spontaneous magnetic transitions and corresponding magnetoelastic properties of intermetallic compounds RMn2Ge2（R=Gd, Tb and Dy） were investigated by using the X-ray diffraction method and magnetic measurement. The results showed that the compounds experience two magnetic transitions, namely the second-order paramagnetic to antiferromagnetic transition at temperature TN（TN=368, 423 and 443 K for Gd Mn2 Ge2, Tb Mn2 Ge2 and Dy Mn2 Ge2, respectively） and the first-order antiferromagnetic-ferrimagnetic transition at temperature Tt（Tt=96, 80 and 40 K for Gd Mn2 Ge2, Tb Mn2 Ge2 and Dy Mn2 Ge2, respectively） as the temperature decreases. The temperature dependence of the lattice constant a（T） displays a negative magnetoelastic anomaly at the second-order transition point TN and, at the first-order transition Tt, a increases abruptly for Gd Mn2 Ge2 and Tb Mn2 Ge2, Da/a about 10^（-3）. Nevertheless, the lattice constant c almost does not change at these transition points indicating that such magnetoelastic anomalies are mainly contributed by the Mn-sublattice. The transitions of the magnetoelastic properties are also evidenced on the temperature dependence of magnetic susceptibility χ. The first-order transition behavior at Tt is explained by the Kittel mode of exchange inversion.展开更多
The structure, magnetization, and magnetocrystalline anisotropy wereinvestigated using X-ray diffraction, vibrating sample magnetometer, and AC susceptibility-meter Itis found that the microstructure of (Sm_(0.5)Nd_(0...The structure, magnetization, and magnetocrystalline anisotropy wereinvestigated using X-ray diffraction, vibrating sample magnetometer, and AC susceptibility-meter Itis found that the microstructure of (Sm_(0.5)Nd_(0.5))_2(Fe_(1-x)Co_x)_(17) alloys is an(Sm,Nd)_2(Fe,Co)_(17) phase with the rhombohedral Th_2Zn_(17)-type structure. The Curie temperatureT_c increases with the Co concentration increasing, and the magnetization first increases as the Cocontent increases in (Sm_(0.5)Nd_(0.5))_2(Fe_(1-x)Co_x)_(17) alloys and then decreases slowly. Theeasy magnetization direction (EMD) of (Sm_(0.5)Nd_(0.5))_2(Fe_(0.25)Co_(0.75))_(17) is along thec-axis and a strong enhancement of the crystalline anisotropy energy constant K is produced by theaddition of some Co atoms. The anisotropy energy constant reaches the maximum when x = 0.75 and thendecreases slowly with the Co content further increasing. The(Sm_(0.5)Nd_(0.5))_2(Fe_(0.25)Co_(0.75))_(17) compound is an optical candidate for the new permanentmagnet, which possesses a high magnetization, a high Curie temperature, and a large anisotropy.展开更多
We report the results of magnetic, thermodynamic, transport and magnetocaloric effect (MCE) studies of newly synthesized Gd_(10)Co_(20)Si_(70) alloy. These measurements confirm an antiferromagnetic transition at T_N=9...We report the results of magnetic, thermodynamic, transport and magnetocaloric effect (MCE) studies of newly synthesized Gd_(10)Co_(20)Si_(70) alloy. These measurements confirm an antiferromagnetic transition at T_N=9 K. Both MCE and magnetoresistance (MR) show quadratic dependence on the applied magnetic field, indicating the presence of spin fluctuations in the alloy. The maximum values of the magnetic entropy change determined from the isothermal magnetization data for magnetic field change of 7 and9 T are found to be 10.5 and 15.6 J/kg·K, respectively. As a consequence of the spin fluctuations effect, the MCE peaks are pulled towards high temperature side as asymmetrically broadened peak. The MR attains a large positive value of 73%at 2 K in 8 T. The large MR and reversible MCE make this alloy an attractive multifunctional magnetic material.展开更多
A series of Nd1-yDyyFe11-xTiMx(M=Mo,Si) alloys have been prepared by arc melting and studied by X-ray diffraction and neutron diffraction.All samples are found to crystallize in the ThMn12-type structure.The lattice p...A series of Nd1-yDyyFe11-xTiMx(M=Mo,Si) alloys have been prepared by arc melting and studied by X-ray diffraction and neutron diffraction.All samples are found to crystallize in the ThMn12-type structure.The lattice parameters a and c and unit cell volume V of Nd0.5Dy0.5Fe11-xTiMox alloys increase linearly with increasing content of Mo(x),while the lattice parameters a and c and unit cell volume V of Nd0.5Dy0.5Fe11-xTiSix alloys decrease linearly with increasing content of Si(x).In NdyDy1-yFe11-xTiMx(M=Mo,Si) compounds,Ti and Mo atoms preferentially occupy the 8i sites and Si atoms preferentially occupy the 8j and 8f sites.Magnetic measurements show that the substitution of Fe by either Mo or Si leads to a decrease in the Curie temperature.展开更多
基金Funded by the National Natural Science Foundation of China(Nos.11547186,11604091)the Natural Science Foundation of Hunan Province(No.2018JJ2019)the Research Foundation of Education Bureau of Hunan Province,China(No.16B048)
文摘The spontaneous magnetic transitions and corresponding magnetoelastic properties of intermetallic compounds RMn2Ge2（R=Gd, Tb and Dy） were investigated by using the X-ray diffraction method and magnetic measurement. The results showed that the compounds experience two magnetic transitions, namely the second-order paramagnetic to antiferromagnetic transition at temperature TN（TN=368, 423 and 443 K for Gd Mn2 Ge2, Tb Mn2 Ge2 and Dy Mn2 Ge2, respectively） and the first-order antiferromagnetic-ferrimagnetic transition at temperature Tt（Tt=96, 80 and 40 K for Gd Mn2 Ge2, Tb Mn2 Ge2 and Dy Mn2 Ge2, respectively） as the temperature decreases. The temperature dependence of the lattice constant a（T） displays a negative magnetoelastic anomaly at the second-order transition point TN and, at the first-order transition Tt, a increases abruptly for Gd Mn2 Ge2 and Tb Mn2 Ge2, Da/a about 10^（-3）. Nevertheless, the lattice constant c almost does not change at these transition points indicating that such magnetoelastic anomalies are mainly contributed by the Mn-sublattice. The transitions of the magnetoelastic properties are also evidenced on the temperature dependence of magnetic susceptibility χ. The first-order transition behavior at Tt is explained by the Kittel mode of exchange inversion.
文摘The structure, magnetization, and magnetocrystalline anisotropy wereinvestigated using X-ray diffraction, vibrating sample magnetometer, and AC susceptibility-meter Itis found that the microstructure of (Sm_(0.5)Nd_(0.5))_2(Fe_(1-x)Co_x)_(17) alloys is an(Sm,Nd)_2(Fe,Co)_(17) phase with the rhombohedral Th_2Zn_(17)-type structure. The Curie temperatureT_c increases with the Co concentration increasing, and the magnetization first increases as the Cocontent increases in (Sm_(0.5)Nd_(0.5))_2(Fe_(1-x)Co_x)_(17) alloys and then decreases slowly. Theeasy magnetization direction (EMD) of (Sm_(0.5)Nd_(0.5))_2(Fe_(0.25)Co_(0.75))_(17) is along thec-axis and a strong enhancement of the crystalline anisotropy energy constant K is produced by theaddition of some Co atoms. The anisotropy energy constant reaches the maximum when x = 0.75 and thendecreases slowly with the Co content further increasing. The(Sm_(0.5)Nd_(0.5))_2(Fe_(0.25)Co_(0.75))_(17) compound is an optical candidate for the new permanentmagnet, which possesses a high magnetization, a high Curie temperature, and a large anisotropy.
基金supported by the result of the Project implementation:University Science Park TECHNICOM for Innovation Applications Supported by Knowledge Technology(ITMS:26220220182)by the Research&Development Operational Programme funded by the ERDF and VEGA1/0956/17,VEGA 1/0611/18 and APVV-16-0079
文摘We report the results of magnetic, thermodynamic, transport and magnetocaloric effect (MCE) studies of newly synthesized Gd_(10)Co_(20)Si_(70) alloy. These measurements confirm an antiferromagnetic transition at T_N=9 K. Both MCE and magnetoresistance (MR) show quadratic dependence on the applied magnetic field, indicating the presence of spin fluctuations in the alloy. The maximum values of the magnetic entropy change determined from the isothermal magnetization data for magnetic field change of 7 and9 T are found to be 10.5 and 15.6 J/kg·K, respectively. As a consequence of the spin fluctuations effect, the MCE peaks are pulled towards high temperature side as asymmetrically broadened peak. The MR attains a large positive value of 73%at 2 K in 8 T. The large MR and reversible MCE make this alloy an attractive multifunctional magnetic material.
基金Supported by the National Natural Science Foundation of China (Grant No. 20775088)the Foundation of State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences (Grant No. KF2008-06)
文摘A series of Nd1-yDyyFe11-xTiMx(M=Mo,Si) alloys have been prepared by arc melting and studied by X-ray diffraction and neutron diffraction.All samples are found to crystallize in the ThMn12-type structure.The lattice parameters a and c and unit cell volume V of Nd0.5Dy0.5Fe11-xTiMox alloys increase linearly with increasing content of Mo(x),while the lattice parameters a and c and unit cell volume V of Nd0.5Dy0.5Fe11-xTiSix alloys decrease linearly with increasing content of Si(x).In NdyDy1-yFe11-xTiMx(M=Mo,Si) compounds,Ti and Mo atoms preferentially occupy the 8i sites and Si atoms preferentially occupy the 8j and 8f sites.Magnetic measurements show that the substitution of Fe by either Mo or Si leads to a decrease in the Curie temperature.
