Role of elastic bending stress on magnetism of a manganite thin film studied by polarized neutron reflectometry

We measured the magnetization depth profile of a (La${}_{1-x}$Pr${}_x$)${}_{1-y}$Ca${}_y$MnO${}_3$ ($x$ = 0.60 ± 0.04, $y$ = 0.20 ± 0.03) film using polarized neutron reflectometry as a function of applied elastic bending stress and temperature. We found unequivocal and until now elusive direct evidence that the exclusive application of compressive or tensile bending stress along the magnetic easy axis increases or decreases, respectively, the saturation magnetization of the film. Furthermore, we obtained a coupling coefficient relating strain to the depth-dependent saturation magnetization.

Figure 1

(a) End-view image of the four-point jig (circled) mounted on a cryostat. (b) Side-view schematic representation of applied bending stress. (c) Transport measurements of the film at different applied bending stress or strain: tensile (filled blue triangles), compressive (filled turquoise circles), and no (filled black squares) strain. Open circles and open triangles represents constant $T$ and constant $T$ ratios ($T/T_{IM}$ = $T/T_{MI}$ = 0.93), respectively, at which we simultaneously measured the neutron reflectivities.

Figure 2

PNR measurements from LPCMO film for different applied strains at (a) constant temperature and (b) constant $T/T_{IM}$ while cooling. Reflectivity data at different applied stresses or strains are shifted by a factor of 5 for clarity. (c) and (d) Magnetization $M$ depth profile corresponding to (a) and (b), respectively.

Figure 3

PNR measurements from LPCMO film for different applied strains at (a) constant temperature and (b) constant $T/T_{MI}$ while warming. Reflectivity data at different applied stresses or strains are shifted by a factor of 5 for clarity. (c) and (d) Magnetization depth profile corresponding to (a) and (b), respectively.

Figure 4

(a)–(f) Variation of magnetization as a function of strain at different temperatures of cooling (left panels) and warming (right panels) for different regions of LPCMO film. The lines are the best fits obtained from linear regression. (g) Coupling coefficient γ for different regions at different temperatures.