Magneto-impedance(MI)effects have been observed in amorphous and nanocrystalline Fe_(73.5)CuNb_(3)Si_(13.5)B_(9) ribbons.Large MI values have been obtained in nanocrystalline samples(NCS),but not in as-quenched sample...Magneto-impedance(MI)effects have been observed in amorphous and nanocrystalline Fe_(73.5)CuNb_(3)Si_(13.5)B_(9) ribbons.Large MI values have been obtained in nanocrystalline samples(NCS),but not in as-quenched samples(AQS).The magnetic responses of impedance of nanocrystalline samples share some common features with that of Co-based amorphous wire and ribbon samples.The field dependencies of effective permeability for nanocrystalline samples have shown a sharp change at the anisotropy field.The effective permeability and the hysteresis loops for AQS and NCS have been shown to be responsible for their MI effects.The sensitivity of the magnetic responses in the nanocrystalline sample can reach 50%/Oe.展开更多
Structural,magnetic,and transport properties of perovskite La_(2/3)Ca_(1/_3)Mn_(1-x)Si_(x)O_(3)(x=0,0.025,0.05)have been studied.The incorporation of Si decreases the overall resistivity,but obviously increases the Cu...Structural,magnetic,and transport properties of perovskite La_(2/3)Ca_(1/_3)Mn_(1-x)Si_(x)O_(3)(x=0,0.025,0.05)have been studied.The incorporation of Si decreases the overall resistivity,but obviously increases the Curie temperature(TC),metal-insulator transition temperature(TP),and the magnetoresistance ratio MR(defined as[R(0)-R(H)]/R(0))near room temperature.Comparing with La_(2/3)Ca_(1/_3)MnO_(3)the TC,TP,and MR of the sample with x=0.05 increase by 30,45K,and 20%,respectively.Lattice effects may play a more important role than the magnetic dilution in the case of low Si substitution.展开更多
The hardening mechanism of nanocry st alline Sm_(2)Fe_(15-x)M_(x)Ga_(2)C,as well as the effect of small amounts of Cu and Nb additions on the hardening behavior were reported.It is shown that the hardening mechanism i...The hardening mechanism of nanocry st alline Sm_(2)Fe_(15-x)M_(x)Ga_(2)C,as well as the effect of small amounts of Cu and Nb additions on the hardening behavior were reported.It is shown that the hardening mechanism is mainly of the pinning-type in Sm_(2)Fe_(15-x)M_(x)Ga_(2)C ribbons.Ret ention of pinning-type behavior,with a marginal increase in coercivity was observed for a small addition of Cu.The hardening mechanism is mainly of nucleation-type in Sm_(2)Fe_(15-x)M_(x)Ga_(2)C with a slightly decrease in coercivity.展开更多
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 structure and magnetic properties of sputtered La-Co alloy films have been studied.Less than 10A/m(100mOe)coercivity can be obtained in amorphous La_(100-x)Co_(x) films around x=80 and the coercivity of amorphous ...The structure and magnetic properties of sputtered La-Co alloy films have been studied.Less than 10A/m(100mOe)coercivity can be obtained in amorphous La_(100-x)Co_(x) films around x=80 and the coercivity of amorphous La^(20)Co_(80) film depends on the thickness of the film.The magnetization behaviour has been examined for the films with different compositions through magnetic hysteresis loops.An excellent rectangular magnetic hysteresis loop was obtained for films with thickness less than 60nm.展开更多
The influence of Cr addition on the magnetic moment,Curie temperature and crystallization temperature of amorphous Nd_(4)Fe_(77.5)B_(18.5) alloy was investigated.With increasing Cr content,the magnetization and Curie ...The influence of Cr addition on the magnetic moment,Curie temperature and crystallization temperature of amorphous Nd_(4)Fe_(77.5)B_(18.5) alloy was investigated.With increasing Cr content,the magnetization and Curie temperature decrease,but the crystallization temperature increases.It is found that the substitution of Cr for Fe can enhance greatly the coercivity of crystallized sample.展开更多
The structure,inagnetic and magnetotransport properties of La_(1-x),Pb_(x) MnO bulk manganese oxides prepared by the standard ceramic techniques were investigated by XRD,VSM,ESM and MR measurements.The sintering condi...The structure,inagnetic and magnetotransport properties of La_(1-x),Pb_(x) MnO bulk manganese oxides prepared by the standard ceramic techniques were investigated by XRD,VSM,ESM and MR measurements.The sintering condition and the hole doped concentration x have a strong iniluence&n the magnetic properties and niagnetore-sistance effect.The maximum MR,20%at room temperature under a field of 2 T, was obtained for x=0.4 and the sintered temperature T_(3)=1260℃.The correlation among the structure,magnetic and MR is discussed.展开更多
The magnetic properties of melt-spun(Fe_(1-x)Nd_(x))_(94)B_(6) alloys(x=0.07-0.90)are reported.Their spontaneous magnetizations are interpreted on the basis of a sperimagnetic structure with Nd and Fe cones.The highes...The magnetic properties of melt-spun(Fe_(1-x)Nd_(x))_(94)B_(6) alloys(x=0.07-0.90)are reported.Their spontaneous magnetizations are interpreted on the basis of a sperimagnetic structure with Nd and Fe cones.The highest coercivity at room temperature is 8 kOe for this as-quenched amorphous alloy system.展开更多
We measured lifetime and doppler broadening spectra of Sm_(2/3)Sr_(1/3)MnO_(3+δ) as functions of temperature by positron annihilation technology In terms of lifetime spectrum,we found that the lattice effects trigger...We measured lifetime and doppler broadening spectra of Sm_(2/3)Sr_(1/3)MnO_(3+δ) as functions of temperature by positron annihilation technology In terms of lifetime spectrum,we found that the lattice effects triggered by ferromagnetic transition give rise to the change of the coefficient of the average linear thermal expansion of Sm_(2/3)Sr_(1/3)MnO_(3+δ) at Tc.In terms of doppler broadening spectrum,we found the delocalization of low-momentum electrons occurs in Sm_(2/3)Sr_(1/3)MnO_(3+δ) at metal-insulator transition temperature.展开更多
High field magnetization and thermomagnetic effects in the as-quenched and heat treated Fe_(78)Nd_(16)B_(6) alloys at different annealing temperatures and time are reported.There are two Curie temperatures to the as-q...High field magnetization and thermomagnetic effects in the as-quenched and heat treated Fe_(78)Nd_(16)B_(6) alloys at different annealing temperatures and time are reported.There are two Curie temperatures to the as-quenched sample.The temperature dependence of coercivity shows a maximum at around 180K for the as-quenched and heat treated samples.A coercive field of 14.8kOe and an energy product of 10MGOe are obtained at romm temperature by annealing at 600℃for 5min.Studies of magnetic anomaly at lower temperature have also been carried out.展开更多
基金Supported by the National Natural Science Foundation of ChinaDoctoral Program Foundation of National Education Commission of China.
文摘Magneto-impedance(MI)effects have been observed in amorphous and nanocrystalline Fe_(73.5)CuNb_(3)Si_(13.5)B_(9) ribbons.Large MI values have been obtained in nanocrystalline samples(NCS),but not in as-quenched samples(AQS).The magnetic responses of impedance of nanocrystalline samples share some common features with that of Co-based amorphous wire and ribbon samples.The field dependencies of effective permeability for nanocrystalline samples have shown a sharp change at the anisotropy field.The effective permeability and the hysteresis loops for AQS and NCS have been shown to be responsible for their MI effects.The sensitivity of the magnetic responses in the nanocrystalline sample can reach 50%/Oe.
基金Supported by National Natural Science Foundation of China under Grant Nos.59702011 and 59525101the 973 State Key Program of Basic Research of China(G1998061314).
文摘Structural,magnetic,and transport properties of perovskite La_(2/3)Ca_(1/_3)Mn_(1-x)Si_(x)O_(3)(x=0,0.025,0.05)have been studied.The incorporation of Si decreases the overall resistivity,but obviously increases the Curie temperature(TC),metal-insulator transition temperature(TP),and the magnetoresistance ratio MR(defined as[R(0)-R(H)]/R(0))near room temperature.Comparing with La_(2/3)Ca_(1/_3)MnO_(3)the TC,TP,and MR of the sample with x=0.05 increase by 30,45K,and 20%,respectively.Lattice effects may play a more important role than the magnetic dilution in the case of low Si substitution.
基金Supported by the National Natural Science Foundation of China under Grant Nos.59525101 and 59771024.
文摘The hardening mechanism of nanocry st alline Sm_(2)Fe_(15-x)M_(x)Ga_(2)C,as well as the effect of small amounts of Cu and Nb additions on the hardening behavior were reported.It is shown that the hardening mechanism is mainly of the pinning-type in Sm_(2)Fe_(15-x)M_(x)Ga_(2)C ribbons.Ret ention of pinning-type behavior,with a marginal increase in coercivity was observed for a small addition of Cu.The hardening mechanism is mainly of nucleation-type in Sm_(2)Fe_(15-x)M_(x)Ga_(2)C with a slightly decrease in coercivity.
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Supported by the National Natural Science Foundation of China under Grant Nos.59471018 and 59392800the U.S.National Science Foundation Grant DMR-9222976 and OSR-1255255.
文摘The structure and magnetic properties of sputtered La-Co alloy films have been studied.Less than 10A/m(100mOe)coercivity can be obtained in amorphous La_(100-x)Co_(x) films around x=80 and the coercivity of amorphous La^(20)Co_(80) film depends on the thickness of the film.The magnetization behaviour has been examined for the films with different compositions through magnetic hysteresis loops.An excellent rectangular magnetic hysteresis loop was obtained for films with thickness less than 60nm.
基金Supported by the State Key Laboratory of Magnetism,Institute of Physics,Chinese Academy of Sciences.
文摘The influence of Cr addition on the magnetic moment,Curie temperature and crystallization temperature of amorphous Nd_(4)Fe_(77.5)B_(18.5) alloy was investigated.With increasing Cr content,the magnetization and Curie temperature decrease,but the crystallization temperature increases.It is found that the substitution of Cr for Fe can enhance greatly the coercivity of crystallized sample.
文摘The structure,inagnetic and magnetotransport properties of La_(1-x),Pb_(x) MnO bulk manganese oxides prepared by the standard ceramic techniques were investigated by XRD,VSM,ESM and MR measurements.The sintering condition and the hole doped concentration x have a strong iniluence&n the magnetic properties and niagnetore-sistance effect.The maximum MR,20%at room temperature under a field of 2 T, was obtained for x=0.4 and the sintered temperature T_(3)=1260℃.The correlation among the structure,magnetic and MR is discussed.
文摘The magnetic properties of melt-spun(Fe_(1-x)Nd_(x))_(94)B_(6) alloys(x=0.07-0.90)are reported.Their spontaneous magnetizations are interpreted on the basis of a sperimagnetic structure with Nd and Fe cones.The highest coercivity at room temperature is 8 kOe for this as-quenched amorphous alloy system.
文摘We measured lifetime and doppler broadening spectra of Sm_(2/3)Sr_(1/3)MnO_(3+δ) as functions of temperature by positron annihilation technology In terms of lifetime spectrum,we found that the lattice effects triggered by ferromagnetic transition give rise to the change of the coefficient of the average linear thermal expansion of Sm_(2/3)Sr_(1/3)MnO_(3+δ) at Tc.In terms of doppler broadening spectrum,we found the delocalization of low-momentum electrons occurs in Sm_(2/3)Sr_(1/3)MnO_(3+δ) at metal-insulator transition temperature.
文摘High field magnetization and thermomagnetic effects in the as-quenched and heat treated Fe_(78)Nd_(16)B_(6) alloys at different annealing temperatures and time are reported.There are two Curie temperatures to the as-quenched sample.The temperature dependence of coercivity shows a maximum at around 180K for the as-quenched and heat treated samples.A coercive field of 14.8kOe and an energy product of 10MGOe are obtained at romm temperature by annealing at 600℃for 5min.Studies of magnetic anomaly at lower temperature have also been carried out.
