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Magnetic Coupling in La0.67 Ca0.33 MnO3/La0.67 Sr0.33 CoO3/La0.67 Ca0.33MnO3 Trilayer Films 总被引:1,自引:0,他引:1
The perovskite La0.67 Ca0.33 MnO3/La0.67 Sr0.33 CoO3/La0.67 Ca0.33 MnO3 trilayers were fabricated by a facing-target sputtering technique and their magnetotransport properties were investigated. The magnetoresistance is dependent on spacer thickness and dramatically decreases when La0.67 Sr0.33 CoO3 layer is thick enough because of its short-circuiting effect. Different from La0.67 Ca0.33 MnO3 single layer, trilayer films with thin La0.67 Sr0.33 CoO3 spacer have the enhanced metal-semiconductor transition temperature (TMS) of La0.67 Ca0.33 MnO3 layers. The magnetic coercivity Hc shows a nonmonotonic behavior with changing the spacer layer thickness at 230 K. The waist-like hysteresis indicates that there is an indirect exchange coupling between the top and bottom Lao.67 Ca0.33 MnO3 layers across the spacer La0.67 Sr0.33 CoO3 layer. 相似文献
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Lattice strain in thin films induced by film-sub-strate mismatchis one source for variant magnetic andresistive behaviors especiallyfor the manganite perovs-kites for which the lattice effects are wellestablished[1~5].It has been also reported that low-fi… 相似文献
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Inrecentyears,muchattentionhasbeenpaidto therare earthdopedmanganitesduetotheirextraor dinarymagneticandtransportproperties.Onone hand,itisbecausetheirabundantelectronicstructure andmagneticproperties[1];ontheotherhand,they exhibitcolossalmagnetoresistan… 相似文献
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The extraordinary colossal magnetoresistance (CMR) behavior in was found that the substitution with Cr on Mn sites introduces an additional bump in zero-field resistivity. With increasing Cr content, this additional bump grows up drastically while the original resistivity peak associated with magnetic order transition diminishes gradually. Under the applied magnetic field, both bumps of resistivity are deeply compressed, which leads to the appearance of two peaks in CMR response. As a result, the temperature range of CMR response is significantly broadened, spanned from the lowest to near room temperature. These results suggest that Mn-site element substitution could be a potent way of tuning CMR response. 相似文献
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Large Magnetic Entropy Effect in La2/3Ca1/3MnO3 总被引:2,自引:0,他引:2
彭振生 《中国稀土学报(英文版)》2004,22(2):232-234
The magnetocaloric effect in the colossal magnetoresistance material La2/3Ca1/3MnO3 was studied. From the measurements of temperature dependence of magnetization in various magnetic fields, the large magnetic entropy change associated with the ferromagnetic-paramagnetie transition was discovered. This result suggests that perovskite manganites are suitable candidates as working substance in magnetie refrigeration technology. 相似文献
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A remarkable CER(colossal electroresistance) effect was observed in a series of polycrystalline Nd0.67Sr0.33MnO3 samples synthe-sized by high energy ball milling successive heat treatment.The CER ratio increased with increasing heating time and reached 3580% at a low temperature for the Nd0.67Sr0.33MnO3 ceramic annealed up to 13 h as measuring current was enhanced from 5 to 500 μA.The result showed that the CER effect was strongly dependent on the sample's microstructure,especially on the foreign phases whi... 相似文献
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La0.8Te0.2MnO3/YBa2Cu3O7-δ(F/S)bilayers were fabricated by electrophoretic technique. The thickness of La0.8Te0.2MnO3 is ~70 μm, the dimensions of YBa2Cu3O7-δ superconductor are 5 mm×10 mm×0.5 mm. The image of cross-sectional profile was measured by scanning electron microscopy (SEM). Standard four-probe method was used for YBa2Cu3O7-δ superconducting resistance measurements. Either 1 mA current is injected from S layer to F layer ( Iinj) or from F layer to S layer (-Iinj),the normal resistance is lower than that without current injection. The critical transition temperature is higher than that without current injection. 相似文献
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La0.67–xDyxPb0.33MnO3(x=0.00 and x=0.10) were elaborated by the solid state method and checked by X-ray diffraction. Close to magnetic temperature transition, the order transition and the critical behavior were investigated by dc magnetization measurements versus x composition. The critical properties were investigated through various techniques such as modified Arrott plot(MAP), Kouvel-Fisher(KF) method and critical isotherm(CI) analysis based on the data of static magnetic measurements recorded around the Curie temperature TC. The values of critical exponents(β and γ) estimated were found to lie between those predicted for a 3D-Ising model for x=0.00 and those of 3D-Heisenberg model for x=0.10. The reliability of the critical exponent’s values was confirmed by the Widom scaling relation and the universal scaling hypothesis. The change in the universality class should be due to the increase of the Dy content. 相似文献
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Lü Huibin 《中国稀土学报(英文版)》2005,23(5):526-529
Theperovskitemanganitehavebeeninvestigated becauseoftheirinterestingpropertiesfullofvariety,includingferromagnetism,antiferromagnetism,metal insulatortransition,highTCsuperconductivity,colos salmagnetoresistanceandsoon,dependingonthe carrierconcentrationd… 相似文献
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The effects of Al ion doping on the Mn site were studied for the colossal magnetoresistance material La0.67Ca0.33MnO3. It is found that the volume of the crystal cell decreases monotonically when the population of Al3 increases across the entire doping range. As the Al3 population increases, the resistance of the material rises rapidly, while the insulator-metal transition temperature TIM decreases linearly. At small Al3 dosage, a thermal activation model properly describes the transport properties at T>TIM, while a metallic model is more suitable at T相似文献
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Magneticanisotropyhasbeenfoundinmanyex oticmaterials,suchasmetallicsuperlatticeswithgi antmagnetoresistanceeffectsandthehightempera turesuperconductingoxideYBa2Cu3O7 δ[1~4].The anisotropycouldfindnovelusesinnewdeviceappli cations.Agoodexampleisthehig… 相似文献
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Porous ceramic samples of Y doped perovskite manganites were prepared. In these samples, the transition from high temperature paramagnetic insulator to low temperature ferromagnetic metal as well as the low field magnetoresistance (LFMR) effect at the low temperature is similar to that in dense samples. Opposite to that in dense samples, LFMR effect in porous sample is observed at the high temperature close to the peak of MR-T curves. The results suggest that the high temperature LFMR effect and the applicable colossal magnetoresistance (CMR) materials could be obtained by controlling the microstructures of this class of perovskite manganites. 相似文献
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CompoundsofthetypeLn1-xAxMnO3(Ln =rareearth ,A =Ca ,Ba ,Sr ,etc .)havebeenthepopularsubjectsofextensiveresearchrecently ,mainlyduetotheexistenceofcolossalmagnetoresistance(CMR ) [1~ 3] .Atroomtemperature ,theperovskitecompoundLnMnO3isantiferromagneticinsulatorwhereMnistrivalent .ThepartialsubstitutionoftrivalentLnionswithdivalentionssuchasCa ,Ba ,Sr ,andPbetc .yieldsanewcompoundexhibitingstrongferro magnetismandhighmetallicconductivity .Thetrans portpropertyinthesecompoundscanbepartly… 相似文献