Thickness dependent transport properties of compressively strained La0.88Sr0.12MnO3 ultrathin films

Thickness dependent magnetic and transport properties of compressively strained La0.88Sr0.12MnO3 thin films grown on single crystalline SrTiO3 (100) substrates have been studied. All films exhibit a large enhancement of ∼130 K in TC/TIM as compared to that of the bulk target (TC∼175 K). This has been explained in terms of suppression of the cooperative Jahn–Teller distortion due to in-plane compressive strain. The TC/TIM of the 5 nm film is 315 K/318 K and slightly increases for film thicknesses ≤25 nm. At higher film thicknesses, ∼60 nm, the TC/TIM starts decreasing. At T>TIM, the electrical transport is due to thermally activated hopping of small polarons. The activation energy is found to be sensitive to film thickness and shows a minimum at around L∼15–25 nm, which corresponds to the maximum of TC/TIM. All films possess large magnetoresistances (MRs) in the vicinity of room temperature. Low as well as high field MRs are observed to nearly double as the film thickness increases from 5 nm (MR∼28%/3 T) to 60 nm (MR%∼50%/3 T). Thicker films (L≥25 nm) are found to exhibit sufficiently large temperature coefficients of resistivities, ∼4%–5%/K, which could be suitable for bolometric applications.