The magnetism and CMR effects of FeCr2-xGaxS4 materials without double-exchange interaction are studied in this paper. The experimental results show that the ferromagnetism of system is strengthened and Tc is raised b...The magnetism and CMR effects of FeCr2-xGaxS4 materials without double-exchange interaction are studied in this paper. The experimental results show that the ferromagnetism of system is strengthened and Tc is raised because the substitution of Ga for Cr ions destroys the interaction among Cr spins in Cr sub-lattice. But the amplitude of PM-FM phase transition decreases gradually with increasing Ga content. The electron spin resonance (ESR) measurements indicate that at temperatures below Tc, the spins in both Fe sub-lattice and Cr sub-lattice are ferromagnetic, while the spins between two sub-lattices are in AFM arrangement. For undoped sample, the macro magnetic moment of Fe sub-lattice and that of Cr sub-lattice cancel out each other. After doping, the net ferromagnetism is introduced at temperatures below Tc; thus the peak temperature of MR curve increases and the value of MR decreases.展开更多
The doping effects of Sm in La 0.67 Ca 0.33 MnO 3 oxide were studied. The results show that with increasing the doping amount of Sm the phase transition temperature of metal insulator for the materials decre...The doping effects of Sm in La 0.67 Ca 0.33 MnO 3 oxide were studied. The results show that with increasing the doping amount of Sm the phase transition temperature of metal insulator for the materials decreases monotonically, the corresponding peak resistance increases rapidly, the Curie temperature decreases monotonically, and the magneto resistance ratio increases quickly. The effects of Sm doping can be explained in terms of lattice effects.展开更多
用磁控溅射方法制备了La0.5Sr0.5MnO3薄膜,研究了薄膜的输运特性和光诱导效应. La0.5Sr0.5MnO3薄膜具有温度相变特征:低温为铁磁金属相,高温则为顺磁非导体相,相变温度420 K. 为铁磁金属相时,光诱导效应导致薄膜的电阻增大,在360 K电阻...用磁控溅射方法制备了La0.5Sr0.5MnO3薄膜,研究了薄膜的输运特性和光诱导效应. La0.5Sr0.5MnO3薄膜具有温度相变特征:低温为铁磁金属相,高温则为顺磁非导体相,相变温度420 K. 为铁磁金属相时,光诱导效应导致薄膜的电阻增大,在360 K电阻变化相对值的最大值约为9.62%.根据双交换作用模型,激光导致顺磁非导体相小极化子的浓度增加,使电阻减小.展开更多
La 0.7 Sr 0.3 Fe x Mn 1- x O 3 compounds (0 05≤ x ≤0 18) were prepared by the sol gel technique. The effects of Fe doping on the magnetic properties, conductivity and magnetoresistance for L...La 0.7 Sr 0.3 Fe x Mn 1- x O 3 compounds (0 05≤ x ≤0 18) were prepared by the sol gel technique. The effects of Fe doping on the magnetic properties, conductivity and magnetoresistance for La 0.7 Sr 0.3 MnO 3 was investigated. Experimental results indicate that the Fe doping leads to a decrease in the ferromagnetic ordering temperature, an increase in the resistance and magnetoresistance effect. For samples of x =0 05 and x =0 08 two peaks are observed in their ρ T curve. Magnetic resistivity ( MR ) of La 0.7 Sr 0.3 Fe 0.08 Mn 0.92 O 3 sample is capable of reaching 18%(8×10 5A·m -1 , 293 K). At x ≥0 1, metal insulator (M I) transition temperature ( T p) is lower than ferromagnetic Curie temperature ( T C) by about 50～80 K.展开更多
基金This work was supported by the National Natural Science Foundation of China (Grant No. 19934003) the Foundation of the Chinese Academy of Sciences and the Research Fund for the Doctoral Program of Higher Education.
文摘The magnetism and CMR effects of FeCr2-xGaxS4 materials without double-exchange interaction are studied in this paper. The experimental results show that the ferromagnetism of system is strengthened and Tc is raised because the substitution of Ga for Cr ions destroys the interaction among Cr spins in Cr sub-lattice. But the amplitude of PM-FM phase transition decreases gradually with increasing Ga content. The electron spin resonance (ESR) measurements indicate that at temperatures below Tc, the spins in both Fe sub-lattice and Cr sub-lattice are ferromagnetic, while the spins between two sub-lattices are in AFM arrangement. For undoped sample, the macro magnetic moment of Fe sub-lattice and that of Cr sub-lattice cancel out each other. After doping, the net ferromagnetism is introduced at temperatures below Tc; thus the peak temperature of MR curve increases and the value of MR decreases.
文摘The doping effects of Sm in La 0.67 Ca 0.33 MnO 3 oxide were studied. The results show that with increasing the doping amount of Sm the phase transition temperature of metal insulator for the materials decreases monotonically, the corresponding peak resistance increases rapidly, the Curie temperature decreases monotonically, and the magneto resistance ratio increases quickly. The effects of Sm doping can be explained in terms of lattice effects.
文摘用磁控溅射方法制备了La0.5Sr0.5MnO3薄膜,研究了薄膜的输运特性和光诱导效应. La0.5Sr0.5MnO3薄膜具有温度相变特征:低温为铁磁金属相,高温则为顺磁非导体相,相变温度420 K. 为铁磁金属相时,光诱导效应导致薄膜的电阻增大,在360 K电阻变化相对值的最大值约为9.62%.根据双交换作用模型,激光导致顺磁非导体相小极化子的浓度增加,使电阻减小.
基金Project Supported by the National Science Foundation of China (19934003)the State Key Project of Fundamental Research of China(001CB610604)+1 种基金the State Key Project of Fundamental Research of China (2007CB925001)the Natural Science Foundation of the Anhui Higher Education Institutions of China(2006KJ266B, ZD2007003-1)
文摘La 0.7 Sr 0.3 Fe x Mn 1- x O 3 compounds (0 05≤ x ≤0 18) were prepared by the sol gel technique. The effects of Fe doping on the magnetic properties, conductivity and magnetoresistance for La 0.7 Sr 0.3 MnO 3 was investigated. Experimental results indicate that the Fe doping leads to a decrease in the ferromagnetic ordering temperature, an increase in the resistance and magnetoresistance effect. For samples of x =0 05 and x =0 08 two peaks are observed in their ρ T curve. Magnetic resistivity ( MR ) of La 0.7 Sr 0.3 Fe 0.08 Mn 0.92 O 3 sample is capable of reaching 18%(8×10 5A·m -1 , 293 K). At x ≥0 1, metal insulator (M I) transition temperature ( T p) is lower than ferromagnetic Curie temperature ( T C) by about 50～80 K.
