Investigation of Magnetoresistance and Its Anisotropy of Thin Polycrystalline La_0.83Sr_0.17MnO₃Films in High Pulsed Magnetic Fields

Abstract

The results on the study of grain boundary effects and influence of film deposition conditions on the magnetoresistance and its anisotropy in polycrystalline La0.83Sr0.17MnO3 films are presented. The magnetoresistance was measured in high pulsed magnetic fields up to 25 T (pulse duration ≈ 0.6 ms) in the temperature range of 120-300 K. A modified Mott hopping model was applied to describe the main behavior of high-field magnetoresistance for both ferromagnetic and paramagnetic phases of the polycrystalline films by taking into account the demagnetization field of the films measured in low magnetic fields perpendicular to film plane. It was also found that to obtain the higher magnetoresistance saturation field at room temperature it is necessary to use the films with smaller crystallites (D ≈ 100 nm). Such films could be used for design of megagauss pulsed magnetic field sensors.

Relation between thickness, crystallite size and magnetoresistance of nanostructured La1−xSrxMnyO3±δ films for magnetic field sensors

“…4). It is known that in thin manganite films the direction of the easy axis of magnetization is parallel to the film plane due to the fact that the demagnetization field is directly linked with the geometric shape of the sample [15–16]. In our case, this effect is partly compensated by the columnar structure of the film, where each individual crystallite has the easy axis of magnetization directed perpendicular to the film plane.…”

“…The manganite films consisting of columnar nanograins have already been successfully applied for the sensing of high pulsed magnetic fields (B-scalar sensor) [13–14]. Despite this development, the scalar (independent of field orientation) CMR effect under a low magnetic field is still a challenging goal towards practical applications due to low sensitivity and large magnetic anisotropy [15–16]. For this reason, the investigation and control of the magnetoresistive properties of manganite materials on the nanometer scale is of great importance.…”

Ageing effects on electrical resistivity and magnetoresistance of nanostructured manganite films

“…3a). It is known that the demagnetisation field is high due to the high aspect ratio of the sample [18]. However, the long-range ferromagnetic order at low temperatures is found only in single crystals or epitaxial films.…”

Accelerated ageing effects in nanostructured La0.83Sr0.17MnO3 films

“…Moreover, for the application of the CMR-B-scalar sensors for measurements of smaller magnetic fields (b 0.5 T), the role of magnetoresistance anisotropy (MRA) significantly increases [2]. It was demonstrated that the main reason of the MRA in thin polycrystalline films is demagnetization effect [10]. This phenomenon increases inaccuracy of measurement of magnetic field magnitude at low fields.…”

“…This phenomenon increases inaccuracy of measurement of magnetic field magnitude at low fields. In thin polycrystalline films the demagnetization effect depends not only on the aspect ratio of the film, but also on the magnetic interaction between grains in film plane [8,10]. Magnetic decoupling is thought to be the result of interfacial effects of grains and depends on grain boundary (GB) material which might be assumed as ferromagnetic regions with suppressed magnetic order [11] due to a high number of various defects, created during film deposition process.…”