Texture evolution in nanocomposite Nd_2Fe_ 14B/α-Fe magnets prepared by direct melt spinning was investigated. The free surface and wheel-contacted surface exhibit different texture direction. Modification of composi...Texture evolution in nanocomposite Nd_2Fe_ 14B/α-Fe magnets prepared by direct melt spinning was investigated. The free surface and wheel-contacted surface exhibit different texture direction. Modification of composition not only enhances magnetic properties, but also changes texture direction of the ribbon. Low temperature heat treatment can increase the magnetic properties to some extent, and high temperature annealing decreases the magnetic properties. Both low and high temperature heat treatment have effects on grain orientation, but the difference still exists between the two surfaces of the ribbon. So it is infeasibility to prepare anisotropic Nd_2Fe_ 14B/α-Fe nanocomposite magnets by direct melt spinning.展开更多
Based on the observation of temperature variation of both domain structure and magnetic con- trast.the thermal demagnetization and randomness of domain nucleation was discussed.
Easy and hard magnetization curves of Nd_2Co_(14)B compound have been measured with extracting-sample-magnetometer(μ_0H_(max)=6T)at 10～300 K.Magnetic anisotropy constants K_1 and K_2 have been determined by fitting ...Easy and hard magnetization curves of Nd_2Co_(14)B compound have been measured with extracting-sample-magnetometer(μ_0H_(max)=6T)at 10～300 K.Magnetic anisotropy constants K_1 and K_2 have been determined by fitting the hard magnetization curves,in which only K_1 ,K_2 and misalignment angle have been taken as fitting parameters.The values of K_1 and K_2 at 4.2 K were derived by extrapolation. Anisotropy coefficients,x_2~° and x_4~°were derived from the anisotropy constants.The anisotropy constant K_2 increases rapidly with increasing temperature when T<T_(sr)and slowly when T>T_(sr).The temperature depen- dence of the magnetic anisotropy coefficient x_2~° was fitted with the formula.The anisotropy coefficients x_2~° can be well described by the tenth-power law from 4.2 K to T_(sr)and by the sixth-power law from T_(sr_ to 300 K.展开更多
A series of magnetic properties of Tm_2Fe_(14)B are explained quantitatively by the calculations based on the single ion model. The magnetic properties include the temperature dependence of the spontaneous magnetizati...A series of magnetic properties of Tm_2Fe_(14)B are explained quantitatively by the calculations based on the single ion model. The magnetic properties include the temperature dependence of the spontaneous magnetization, the spin reorientation temperature and the magnetization curves along the principal crystal axes at 4.2, 100, 150 and 200 K. The values of the exchange field and the crystalline electric field parameters used in the calculations are μ_BH_(ex)(T=0 K)=135, B_2~0=1.77, B_2~2=±2.97, B_4~0=-3.06×10^(-3), B_4^(-2)=0, B_4~4=-6.82×10^(-3), B_6~0=1.05× 10^(-5), B_6^(-2)=±7.40×10^(-5), B_6~4=1.96×10^(-4), and B_6^(-6)=0 all in K unit. The magnetization processes of the Fe-and Tm-sublattices at different temperatures are analysed. The processes are characterized by the non-collinearity between the magnetic moments of the Fe-and Tm-sublattices.展开更多
文摘Texture evolution in nanocomposite Nd_2Fe_ 14B/α-Fe magnets prepared by direct melt spinning was investigated. The free surface and wheel-contacted surface exhibit different texture direction. Modification of composition not only enhances magnetic properties, but also changes texture direction of the ribbon. Low temperature heat treatment can increase the magnetic properties to some extent, and high temperature annealing decreases the magnetic properties. Both low and high temperature heat treatment have effects on grain orientation, but the difference still exists between the two surfaces of the ribbon. So it is infeasibility to prepare anisotropic Nd_2Fe_ 14B/α-Fe nanocomposite magnets by direct melt spinning.
文摘Based on the observation of temperature variation of both domain structure and magnetic con- trast.the thermal demagnetization and randomness of domain nucleation was discussed.
基金This work has been supported by the National Natural Science Foundation of P.R.China(5870025)Magnetism Laboratory of Institute of Physics,Beijing,P.R.China.
文摘Easy and hard magnetization curves of Nd_2Co_(14)B compound have been measured with extracting-sample-magnetometer(μ_0H_(max)=6T)at 10～300 K.Magnetic anisotropy constants K_1 and K_2 have been determined by fitting the hard magnetization curves,in which only K_1 ,K_2 and misalignment angle have been taken as fitting parameters.The values of K_1 and K_2 at 4.2 K were derived by extrapolation. Anisotropy coefficients,x_2~° and x_4~°were derived from the anisotropy constants.The anisotropy constant K_2 increases rapidly with increasing temperature when T<T_(sr)and slowly when T>T_(sr).The temperature depen- dence of the magnetic anisotropy coefficient x_2~° was fitted with the formula.The anisotropy coefficients x_2~° can be well described by the tenth-power law from 4.2 K to T_(sr)and by the sixth-power law from T_(sr_ to 300 K.
文摘A series of magnetic properties of Tm_2Fe_(14)B are explained quantitatively by the calculations based on the single ion model. The magnetic properties include the temperature dependence of the spontaneous magnetization, the spin reorientation temperature and the magnetization curves along the principal crystal axes at 4.2, 100, 150 and 200 K. The values of the exchange field and the crystalline electric field parameters used in the calculations are μ_BH_(ex)(T=0 K)=135, B_2~0=1.77, B_2~2=±2.97, B_4~0=-3.06×10^(-3), B_4^(-2)=0, B_4~4=-6.82×10^(-3), B_6~0=1.05× 10^(-5), B_6^(-2)=±7.40×10^(-5), B_6~4=1.96×10^(-4), and B_6^(-6)=0 all in K unit. The magnetization processes of the Fe-and Tm-sublattices at different temperatures are analysed. The processes are characterized by the non-collinearity between the magnetic moments of the Fe-and Tm-sublattices.
