中国物理B ›› 2021, Vol. 30 ›› Issue (9): 97502-097502.doi: 10.1088/1674-1056/ac012d

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Current-dependent positive magnetoresistance inLa0.8Ba0.2MnO3 ultrathin films

Guankai Lin(林冠凯)1, Haoru Wang(王昊儒)1, Xuhui Cai(蔡旭晖)1, Wei Tong(童伟)2, and Hong Zhu(朱弘)1,3,†   

  1. 1 Department of Physics, University of Science and Technology of China, Hefei 230026, China;
    2 Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory of the Chinese Academy of Sciences, Hefei 230031, China;
    3 Key Laboratory of Strongly-Coupled Quantum Matter Physics, Chinese Academy of Sciences, Hefei 230026, China
  • 收稿日期:2021-03-24 修回日期:2021-05-08 接受日期:2021-05-14 出版日期:2021-08-19 发布日期:2021-08-19
  • 通讯作者: Hong Zhu E-mail:zhuh@ustc.edu.cn
  • 基金资助:
    Project supported by the National Natural Science Foundation of China (Grant No. 11674298), the National Key Research and Development Program of China (Grant No. 2017YFA0403502), and the Users with Excellence Project of Hefei Science Center CAS (Grant No. 2018HSC-UE013).

Current-dependent positive magnetoresistance inLa0.8Ba0.2MnO3 ultrathin films

Guankai Lin(林冠凯)1, Haoru Wang(王昊儒)1, Xuhui Cai(蔡旭晖)1, Wei Tong(童伟)2, and Hong Zhu(朱弘)1,3,†   

  1. 1 Department of Physics, University of Science and Technology of China, Hefei 230026, China;
    2 Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory of the Chinese Academy of Sciences, Hefei 230031, China;
    3 Key Laboratory of Strongly-Coupled Quantum Matter Physics, Chinese Academy of Sciences, Hefei 230026, China
  • Received:2021-03-24 Revised:2021-05-08 Accepted:2021-05-14 Online:2021-08-19 Published:2021-08-19
  • Contact: Hong Zhu E-mail:zhuh@ustc.edu.cn
  • Supported by:
    Project supported by the National Natural Science Foundation of China (Grant No. 11674298), the National Key Research and Development Program of China (Grant No. 2017YFA0403502), and the Users with Excellence Project of Hefei Science Center CAS (Grant No. 2018HSC-UE013).

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摘要： We report an investigation into the magnetoresistance (MR) of La0.8Ba0.2MnO3 ultrathin films with various thicknesses. While the 13 nm-thick film shows the commonly reported negative magnetoresistive effect, the 6 nm- and 4 nm-thick films display unconventional positive magnetoresistive (PMR) behavior under certain conditions. As well as the dependence on the film's thickness, it has been found that the electrical resistivity and the PMR effect of the thinner films are very dependent on the test current. For example, the magnetoresistive ratio of the 4 nm-thick film changes from +46% to -37% when the current is increased from 10 nA to 100 nA under 15 kOe at 40 K. In addition, the two thinner films present opposite changes in electrical resistivity with respect to the test current, i.e., the electroresistive (ER) effect, at low temperatures. We discuss the complex magnetoresistive and ER behaviors by taking account of the weak contacts at grain boundaries between ferromagnetic metallic (FMM) grains. The PMR effect can be attributed to the breaking of the weak contacts due to the giant magnetostriction of the FMM grains under a magnetic field. Considering the competing effects of the conductive filament and local Joule self-heating at grain boundaries on the transport properties, the dissimilar ER effects in the two thinner films are also understandable. These experimental findings provide an additional approach for tuning the magnetoresistive effect in manganite films.

关键词: positive magnetoresistance, electroresistance, Joule self-heating, conductive filament

Abstract: We report an investigation into the magnetoresistance (MR) of La0.8Ba0.2MnO3 ultrathin films with various thicknesses. While the 13 nm-thick film shows the commonly reported negative magnetoresistive effect, the 6 nm- and 4 nm-thick films display unconventional positive magnetoresistive (PMR) behavior under certain conditions. As well as the dependence on the film's thickness, it has been found that the electrical resistivity and the PMR effect of the thinner films are very dependent on the test current. For example, the magnetoresistive ratio of the 4 nm-thick film changes from +46% to -37% when the current is increased from 10 nA to 100 nA under 15 kOe at 40 K. In addition, the two thinner films present opposite changes in electrical resistivity with respect to the test current, i.e., the electroresistive (ER) effect, at low temperatures. We discuss the complex magnetoresistive and ER behaviors by taking account of the weak contacts at grain boundaries between ferromagnetic metallic (FMM) grains. The PMR effect can be attributed to the breaking of the weak contacts due to the giant magnetostriction of the FMM grains under a magnetic field. Considering the competing effects of the conductive filament and local Joule self-heating at grain boundaries on the transport properties, the dissimilar ER effects in the two thinner films are also understandable. These experimental findings provide an additional approach for tuning the magnetoresistive effect in manganite films.

Key words: positive magnetoresistance, electroresistance, Joule self-heating, conductive filament

中图分类号:  (Magnetoresistance)

  • 73.43.Qt
84.37.+q (Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)) 52.50.Nr (Plasma heating by DC fields; ohmic heating, arcs) 52.38.Hb (Self-focussing, channeling, and filamentation in plasmas)