The magnetic-field-induced strains (MFIS) of polycrystallineNi_(50)Mn_(29)Ga_(21) alloys containing Tb were studied. A large MFIS of -1.10% was obtained undercompressi ve prestress conditions. The addition of Tb can f...The magnetic-field-induced strains (MFIS) of polycrystallineNi_(50)Mn_(29)Ga_(21) alloys containing Tb were studied. A large MFIS of -1.10% was obtained undercompressi ve prestress conditions. The addition of Tb can fine the crystal grains, enhance thebending strength obviously, and make MFIS increase further, indicating that a moderate amount of Tbdoes not hinder twin boundary motion and it conversely makes the material more practical.展开更多
The coercivity mechanism of Nd-Fe-B based magnets prepared by a new techniqueof strip casting was investigated. Different from the traditional magnets, α-Fe phases aredifficult to be found in Nd-Fe-B magnets prepared...The coercivity mechanism of Nd-Fe-B based magnets prepared by a new techniqueof strip casting was investigated. Different from the traditional magnets, α-Fe phases aredifficult to be found in Nd-Fe-B magnets prepared by strip casting. Meanwhile, the rich-Nd phasesoccur not only near the grain boundaries of main phases, but also within the main-phase grains.Investigation on the magnetizing field dependence of the coercivity for the(Nd_(0.935)Dy_(0.065))_(14.5)Fe_(79.4)B_(6.1) magnet and the temperature dependence of thecoercivity for the Nd_(14.5)Fe_(79.4)B_(6.1) magnet hav been done. Results show that coercivitiesfor strip casting magnets are controlled by the nucleation mechanism.展开更多
The giant magneto-impedance (GMI) effect associated with the variation of transverse permeability for the ribbons Fe89Zr6Hf1B4 with different annealing temperatures T-A = 793, 823, 893, 923, 993, and 1033 K was invest...The giant magneto-impedance (GMI) effect associated with the variation of transverse permeability for the ribbons Fe89Zr6Hf1B4 with different annealing temperatures T-A = 793, 823, 893, 923, 993, and 1033 K was investigated. There is an optimum annealing temperature TA = 993 K for obtaining the largest GMI effect for the ribbons Fe89Zr6Hf1B4. The magneto-impedance GMI (Z) = (Z(H) - Z(0))/Z(0) for the ribbon with T-A = 993 K can reach -55.09% at a frequency f = 900 kHz under H = 7162 A/m. The relative changes of the real part of transverse permeability Delta mu'/mu'(0) = (mu'(H)- mu'(0))/mu'(0) under H = 7162 A center dot m(-1) at f = 1 MHz are -78.83%, -89.98% and -94.77 % for Fe89Zr6Hf1B4 ribbons with T-A = 823, 893, and 993 K, respectively. The strong GMI effect is accompanied by the large change of transverse permeability. A large magnetoreaetance GMI(X) = (X (H) - X (0))/X (0) of -81.09% can be obtained at f = 100 kHz under H = 7162 A/m for the ribbon with T-A = 993 K. Meanwhile, this present result gave an experimental support to the previous concept / assumption that the positive peak in the field dependence of magneto-impedance is connected to the peak of transverse permeability with varying fields.展开更多
The giant magnetoimpedance effect of the nanocrystalline ribbonFe_(84)Zr_(2.08)Nb_(1.92)Cu_1B_(11) (atom fraction in %) was investigated. There is an optimumannealing temperature (T_A≈ 998 K) for obtaining the larges...The giant magnetoimpedance effect of the nanocrystalline ribbonFe_(84)Zr_(2.08)Nb_(1.92)Cu_1B_(11) (atom fraction in %) was investigated. There is an optimumannealing temperature (T_A≈ 998 K) for obtaining the largest GMI (giant magneto-impedance) effectin the ribbon Fe_(84)Zr_(2.08)Nb_(1.92)Cu_1B_(11). The ribbon with longer ribbon length has strongerGMI effect, which may be connected with the demagnetization effect of samples. The frequencyf_(max), where the maximum magnetoimpedance GMI(Z)_(max) = [(Z(H) - Z(0))/Z(0)]_(max) occurs, isnear the intersecting frequency f_i of the curves of GMI(R), GMI(X), and GMI(Z) versus frequency.The magnetoreactance GMI(X) decreases monotonically with increasing frequency, which may be due tothe decrease of permeability. In contrast, with the AC (alternating current) frequency increasing,the inagnetore-sistance GMI(R) increases at first, undergoes a peak, and under then drops. Theincrease of the magnetoresistance may result from the enhancement of the skin effect with frequency.The maximum magnetoimpedance value GMI(Z)_(max) under H = 7.2 kA/m is about -56.18% at f= 0.3 MHzfor the nanocrystalline ribbon Fe_(84)Zr_(2.08)Nb_(1.92)Cu_1B_(11) with the annealing temperatureT_A= 998 K and the ribbon length L = 6 cm.展开更多
基金This work was financially supported by the 863 Program of China (No. 2001AA327022)the Natural Science Foundation of Inner Mongolia (No. 200308020214)
文摘The magnetic-field-induced strains (MFIS) of polycrystallineNi_(50)Mn_(29)Ga_(21) alloys containing Tb were studied. A large MFIS of -1.10% was obtained undercompressi ve prestress conditions. The addition of Tb can fine the crystal grains, enhance thebending strength obviously, and make MFIS increase further, indicating that a moderate amount of Tbdoes not hinder twin boundary motion and it conversely makes the material more practical.
基金This work is supported by the National Natural Science Foundation of China (No. 50271036).
文摘The coercivity mechanism of Nd-Fe-B based magnets prepared by a new techniqueof strip casting was investigated. Different from the traditional magnets, α-Fe phases aredifficult to be found in Nd-Fe-B magnets prepared by strip casting. Meanwhile, the rich-Nd phasesoccur not only near the grain boundaries of main phases, but also within the main-phase grains.Investigation on the magnetizing field dependence of the coercivity for the(Nd_(0.935)Dy_(0.065))_(14.5)Fe_(79.4)B_(6.1) magnet and the temperature dependence of thecoercivity for the Nd_(14.5)Fe_(79.4)B_(6.1) magnet hav been done. Results show that coercivitiesfor strip casting magnets are controlled by the nucleation mechanism.
基金This project was financially supported by the National Natural Science Foundation of China (No. 50271036).
文摘The giant magneto-impedance (GMI) effect associated with the variation of transverse permeability for the ribbons Fe89Zr6Hf1B4 with different annealing temperatures T-A = 793, 823, 893, 923, 993, and 1033 K was investigated. There is an optimum annealing temperature TA = 993 K for obtaining the largest GMI effect for the ribbons Fe89Zr6Hf1B4. The magneto-impedance GMI (Z) = (Z(H) - Z(0))/Z(0) for the ribbon with T-A = 993 K can reach -55.09% at a frequency f = 900 kHz under H = 7162 A/m. The relative changes of the real part of transverse permeability Delta mu'/mu'(0) = (mu'(H)- mu'(0))/mu'(0) under H = 7162 A center dot m(-1) at f = 1 MHz are -78.83%, -89.98% and -94.77 % for Fe89Zr6Hf1B4 ribbons with T-A = 823, 893, and 993 K, respectively. The strong GMI effect is accompanied by the large change of transverse permeability. A large magnetoreaetance GMI(X) = (X (H) - X (0))/X (0) of -81.09% can be obtained at f = 100 kHz under H = 7162 A/m for the ribbon with T-A = 993 K. Meanwhile, this present result gave an experimental support to the previous concept / assumption that the positive peak in the field dependence of magneto-impedance is connected to the peak of transverse permeability with varying fields.
基金This work was financially supported by the National Natural Science Foundation of China (No. 50271036)
文摘The giant magnetoimpedance effect of the nanocrystalline ribbonFe_(84)Zr_(2.08)Nb_(1.92)Cu_1B_(11) (atom fraction in %) was investigated. There is an optimumannealing temperature (T_A≈ 998 K) for obtaining the largest GMI (giant magneto-impedance) effectin the ribbon Fe_(84)Zr_(2.08)Nb_(1.92)Cu_1B_(11). The ribbon with longer ribbon length has strongerGMI effect, which may be connected with the demagnetization effect of samples. The frequencyf_(max), where the maximum magnetoimpedance GMI(Z)_(max) = [(Z(H) - Z(0))/Z(0)]_(max) occurs, isnear the intersecting frequency f_i of the curves of GMI(R), GMI(X), and GMI(Z) versus frequency.The magnetoreactance GMI(X) decreases monotonically with increasing frequency, which may be due tothe decrease of permeability. In contrast, with the AC (alternating current) frequency increasing,the inagnetore-sistance GMI(R) increases at first, undergoes a peak, and under then drops. Theincrease of the magnetoresistance may result from the enhancement of the skin effect with frequency.The maximum magnetoimpedance value GMI(Z)_(max) under H = 7.2 kA/m is about -56.18% at f= 0.3 MHzfor the nanocrystalline ribbon Fe_(84)Zr_(2.08)Nb_(1.92)Cu_1B_(11) with the annealing temperatureT_A= 998 K and the ribbon length L = 6 cm.
