Large Low-Field Magnetoresistance (LFMR) Effect in Free-Standing La_0.7Sr_0.3MnO₃ Films

Abstract

The realization of a large low-field magnetoresistance (LFMR) effect in free-standing magnetic oxide films is a crucial goal toward promoting the development of flexible, low power consumption, and nonvolatile memory devices for information storage. La0.7Sr0.3MnO3 (LSMO) is an ideal material for spintronic devices due to its excellent magnetic and electronic properties. However, it is difficult to achieve both a large LFMR effect and high flexibility in LSMO films due to the lack of research on LFMR-related mechanisms and the strict LSMO growth conditions, which require rigid substrates. Here, we induced a large LFMR effect in an LSMO/mica heterostructure by utilizing a disorder-related spin-polarized tunneling effect and developed a simple transfer method to obtain free-standing LSMO films for the first time. Electrical and magnetic characterizations of these free-standing LSMO films revealed that all of the principal properties of LSMO were sustained under compressive and tensile conditions. Notably, the magnetoresistance of the processed LSMO film reached up to 16% under an ultrasmall magnetic field (0.1 T), which is 80 times that of a traditional LSMO film. As a demonstration, a stable nonvolatile multivalue storage function in flexible LSMO films was successfully achieved. Our work may pave the way for future wearable resistive memory device applications.

Freestanding Perovskite Oxide Films: Synthesis, Challenges, and Properties

“…[ 97 ] The weak interaction between the oxide layers and the substrates offers the opportunity of creating freestanding membranes by exfoliating the top layers. [ 98 ]…”

“…[97] The weak interaction between the oxide layers and the substrates offers the opportunity of creating freestanding membranes by exfoliating the top layers. [98] A characteristic example of 2D-layered material used for the integration of perovskite oxide is mica, a large family of phyllosilicate minerals possessing a monoclinic structure layered along the 001 plane. Mica possesses general formula X 2 Y n Z 8 O 20 (OH,F) 4 , where X, Y and Z are the interlayer cation (e.g., K and Na), the octedrahedrally coordinated atom (e.g., Al and Mg) and the tetrahedral coordinated element (Si, Al, etc.…”

“…[108] These results show that different types of crystallographic orientations and bonding can be expected at the perovskite/mica interface. The possibility of cleaving La 0.7 Sr 0.3 MnO 3 thin films from mica substrates was demonstrated by Zhang et al [98] In their work, the authors showed that polycrystalline LSMO thin films could be easily peeled off by muscovite mica due to the weak interaction between the film and the substrate. Additionally, mica can be cleaved along the weak bonded constitutive planes after the thin film deposition, increasing the flexibility of the structure and allowing the study of bending strain effect on the perovskite layers (see Section 4.2).…”

Bending Modulated Ultralarge Magnetoresistance in Flexible La0.67Ba0.33MnO3 Thin Film Based Device

“…The resistance increasing arises from the distortion of the La 0.67 Ba 0.33 MnO 3 crystal structure, which is similar to the reports in La 0.67 Sr 0.33 MnO 3 and La 0.67 Ca 0.33 MnO 3 systems. 19,24,32 Figure 2c compares the change of resistance ΔR of the film while measured along the bending direction and perpendicular to the bending direction, respectively. Interestingly, apparent enhancement of ΔR can be found while measured along the bending direction.…”

“…F-Mica is a two-dimensional layered substrate with excellent flexibility at thicknesses less than 50 μm . Based on the flexible substrate, several kinds of perovskite oxides like La 0.67 Sr 0.33 MnO 3 , , La 0.67 Ca 0.33 MnO 3 , and SrRuO 3 , have been epitaxially grown with nice crystalline quality. LBMO is a room-temperature MR material with rhombohedral crystalline structure ( a = b = 5.54 Å, c = 13.51 Å, α = β = 90°, γ = 120°) .…”