Electrical properties and magnetoresistance have been studied in two series of xAg-La0.67（Ca0.65Ba0.35）0.33MnO3 and xPd-La0.67（Ca0.65Ba0.35）0.33MnO3 （abbreviated by xAg-LCBMO and xPd-LCBMO） composites. Both Pd a...Electrical properties and magnetoresistance have been studied in two series of xAg-La0.67（Ca0.65Ba0.35）0.33MnO3 and xPd-La0.67（Ca0.65Ba0.35）0.33MnO3 （abbreviated by xAg-LCBMO and xPd-LCBMO） composites. Both Pd and Ag addition induce a decrease in resistivity and an increase in temperature at which the resistivity reaches its maximum. This is mainly due to the improvement of grain boundaries caused by the segregation of good conductive metal grains on the grain boundaries/surfaces. In addition, both Pd and Ag addition induce a large enhancement of room temperature magnetoresistance （RTMR）. Note that 27% molar ratio of Ag addition induces a large RTMR of about 70%, about ten times larger than pure LCBMO, whereas 27% molar ratio Pd addition brings a much larger RTMR of about 170%. The large enhancements of MR can be attributed to the decrease in resistivity of the samples caused by the good conductive metal. On the other hand, the polarization of Pd atoms near the Mn ions on the grain surfaces/boundaries plays a very im-portant role in the increase in MR, which induces a large number of spin clusters in Pd-added samples.展开更多
By measuring M-T curves, ρ-T curves and MR-T curves of the samples under different temperatures, the influence of Dy doping （0.00 ≤ x ≤0.30） on the magnetic and electric properties of La0.7-xDyxSr0.3MnO3 has been...By measuring M-T curves, ρ-T curves and MR-T curves of the samples under different temperatures, the influence of Dy doping （0.00 ≤ x ≤0.30） on the magnetic and electric properties of La0.7-xDyxSr0.3MnO3 has been studied. The experimental results show that, with the increase of the Dy content, the system undergoes a transition from long range ferromagnetic order to the cluster-spin glass state and further to antiferromagnetic order. For the samples with x=0.20 and 0.30, their magnetic behaviors are abnormal at low temperature, and their resistivities at low temperature have a minimum value. These peculiar phenomena not only come from the lattice effect induced by doping, but also from extra magnetic coupling induced by doping.展开更多
The effect of sintering temperature on the structure, magnetic transition and magnetic entropy of La0.6Ca0.4MnO3 manganite was studied. It was observed that this compound belongs to the orthorhombic structure with the...The effect of sintering temperature on the structure, magnetic transition and magnetic entropy of La0.6Ca0.4MnO3 manganite was studied. It was observed that this compound belongs to the orthorhombic structure with the Pnma space group without any impurity phase. The effect of sintering temperature on the Curie temperature(TC) was studied. The small increment in TC is found with increasing the sintering temperature. The magnetocaloric study exposes a quite large change of the magnetic entropy, which varies with sintering temperature. For an applied magnetic field of 3 T and sintering temperature of 1300 °C, the relative cooling power(RCP) is 89 J/kg. As a result, the studied compound can be considered as potential material for magnetic refrigeration near and below room temperature.展开更多
We demonstrate very large and uniform temperature gradients up to about 1 K every 100 nm, in an architecture which is compatible with the field-effect control of the nanostructure under test. The temperature gradients...We demonstrate very large and uniform temperature gradients up to about 1 K every 100 nm, in an architecture which is compatible with the field-effect control of the nanostructure under test. The temperature gradients demonstrated greatly exceed those typically obtainable with standard resistive heaters fabricated on top of the oxide layer. The nanoheating platform is demonstrated in the specific case of a short-nanowire device.展开更多
文摘Electrical properties and magnetoresistance have been studied in two series of xAg-La0.67（Ca0.65Ba0.35）0.33MnO3 and xPd-La0.67（Ca0.65Ba0.35）0.33MnO3 （abbreviated by xAg-LCBMO and xPd-LCBMO） composites. Both Pd and Ag addition induce a decrease in resistivity and an increase in temperature at which the resistivity reaches its maximum. This is mainly due to the improvement of grain boundaries caused by the segregation of good conductive metal grains on the grain boundaries/surfaces. In addition, both Pd and Ag addition induce a large enhancement of room temperature magnetoresistance （RTMR）. Note that 27% molar ratio of Ag addition induces a large RTMR of about 70%, about ten times larger than pure LCBMO, whereas 27% molar ratio Pd addition brings a much larger RTMR of about 170%. The large enhancements of MR can be attributed to the decrease in resistivity of the samples caused by the good conductive metal. On the other hand, the polarization of Pd atoms near the Mn ions on the grain surfaces/boundaries plays a very im-portant role in the increase in MR, which induces a large number of spin clusters in Pd-added samples.
基金This work was supported by the National Nature Science Foundation of China （No. 19934003） the State Key Project of Fundamental Research of China （No.001CB610604） the Item of Nature Science Research of Anhui （No. 2001kj244）.
文摘By measuring M-T curves, ρ-T curves and MR-T curves of the samples under different temperatures, the influence of Dy doping （0.00 ≤ x ≤0.30） on the magnetic and electric properties of La0.7-xDyxSr0.3MnO3 has been studied. The experimental results show that, with the increase of the Dy content, the system undergoes a transition from long range ferromagnetic order to the cluster-spin glass state and further to antiferromagnetic order. For the samples with x=0.20 and 0.30, their magnetic behaviors are abnormal at low temperature, and their resistivities at low temperature have a minimum value. These peculiar phenomena not only come from the lattice effect induced by doping, but also from extra magnetic coupling induced by doping.
基金Project(2012-RIAIB300784) supported by Basic Science Research Program through the NRF of Korea funded by the MESTProject(2012HIB8A2026212) supported by the MEST and NRF of Korea the Human Training Project for Regional Innovation
文摘The effect of sintering temperature on the structure, magnetic transition and magnetic entropy of La0.6Ca0.4MnO3 manganite was studied. It was observed that this compound belongs to the orthorhombic structure with the Pnma space group without any impurity phase. The effect of sintering temperature on the Curie temperature(TC) was studied. The small increment in TC is found with increasing the sintering temperature. The magnetocaloric study exposes a quite large change of the magnetic entropy, which varies with sintering temperature. For an applied magnetic field of 3 T and sintering temperature of 1300 °C, the relative cooling power(RCP) is 89 J/kg. As a result, the studied compound can be considered as potential material for magnetic refrigeration near and below room temperature.
文摘We demonstrate very large and uniform temperature gradients up to about 1 K every 100 nm, in an architecture which is compatible with the field-effect control of the nanostructure under test. The temperature gradients demonstrated greatly exceed those typically obtainable with standard resistive heaters fabricated on top of the oxide layer. The nanoheating platform is demonstrated in the specific case of a short-nanowire device.
