Crossover from negative to positive magnetoresistance in La0.7Ce0.3MnO3-SrTiO3-Nb heterojunctions

Abstract

A crossover from negative to positive magnetoresistance (MR) is observed in the heterojunction composed of a La0.7Ce0.3MnO3 film and a 0.5wt.% Nb-doped SrTiO3 substrate. The temperature and bias current dependences of MR sign in the junction are investigated carefully. It is found that the positive MR occurs when temperature or applied bias current is increased to a higher value. The relation between MR and an external magnetic field is also found to be temperature dependent. We attribute the appearance of the positive MR at higher temperatures to the tunneling transport mechanism. These results are helpful in configuring artificial devices using manganite-based heterojunctions.

Current-perpendicular-to-plane transport properties of polycrystalline Fe3O4/α-Fe2O3 heterostructures

“…At the temperatures in the range of 230-260 K, with increasing current a crossover of MR from negative to positive was observed, consistent with that observed in the Fe 3 O 4 / BaTiO 3 , LaCaMnO/ NSTO, and LaCeMnO/NSTO structures. 3,18,19 At other temperatures, MR value decreases with increasing current because increasing voltage decreases the width of depletion layer, and the contribution of the depletion layer to R junc decreases, resulting in the MR reduction. At temperatures below 180 K, the small increase in MR with current after the sharp decline ͓see Fig.…”

Crossover of magnetoresistance from negative to positive in the heterojunction composed of La0.82Ca0.18MnO3 and 0.5wt% Nb-doped SrTiO3

“…Recently, to utilize the perovskite-type manganites in electronic devices, manganite-based p-n, p-i-n, and organic diodes, such as ͑La, Ba͒MnO 3 /Sr͑Ti, Nb͒O 3 , 1 ͑La, Ca͒MnO 3 / SrTiO 3 / ͑La, Ce͒MnO 3 , 2 and ͑La, Sr͒MnO 3 /organic semiconductor, 3 have been extensively studied, and the magnetically tunable rectifying characteristics of electron-doped perovskite-oxide p-n and p-i-n diodes have been demonstrated. 2,4 The observed negative magnetoresistance ͑MR͒ in the heterojunctions was considered to originate from the negative MR of the manganites. But a few perovskite oxide materials with positive MR or a bias-dependent MR have been also found.…”

Rectifying characteristics, magnetic tunability, and photovoltaic response in La0.8Hf0.2MnO3/0.7 wt% Nb-SrTiO3 heteroepitaxial junctions

“…Among them, La 0.8 Hf 0.2 MnO 3 (LHMO)is a tetravalent cation-doped manganite in which the La 3þ ions are substituted by Hf 4þ ions. 9 Unlike other tetravalent cations, Hf does not have multivalent states (e.g., Ce with a mixed valence state of Ce 3þ and Ce 4þ ), 10,11 thus avoiding the complex and unreliable factors in the research. 12 Therefore, fabrication and studies of LHMO-based heterojunctions could improve our understanding of these complicated systems and promote the application of such heterojunctions.…”