Tunable room temperature low-field spin polarized tunneling magnetoresistance of La0.7Sr0.3MnO3 nanoparticles

The authors have studied low-field spin polarized tunneling magnetoresistance (LFMR) at room temperature of a series of nanocrystalline La0.67Sr0.33MnO3 samples having average crystallite size (phi) from 14 to 150 nm. Interestingly with decrease in phi, LFMR enhances up to a critical phi of 28 nm, beyond which LFMR starts decreasing, indicating a pronounced crossover of LFMR value (LFMRmax similar to 1.67%) with decrease in phi. Magnetization versus magnetic field study at room temperature reveals that with decrease in phi LFMR increases untill the nanoparticles remain magnetically multidomain (MD), but as soon as it falls in the single domain (SD) regime, LFMR immediately starts diminishing. Their study explores the fact that for MD nanoparticles room temperature LFMR is decided only by surface spin susceptibility (chi(b)), whereas for SD nanoparticles LFMR arises as a result of a sensitive balance between chi(b) and thermal effect.