Powered by Indico
v3.2.8
An epitaxial La0.45Sr0.55MnO3 (LSMO) film, which has a paramagnetic-to-ferromagnetic transition at ~260 K and a partial ferromagnetic-to-antiferromagnetic transition at ~140 K upon cooling, was synthesized on (001) (La0.18Sr0.82)(Al0.59Ta0.41)O3 with pulsed laser deposition(PLD). The x-ray diffraction pattern showed interference fringes around the (002) LSMO peak, indicating a successful growth of a high quality and smooth film. When the LSMO film was cooled down in a magnetic field of 5 kOe, it exhibited a large exchange bias (HEX) of ~490 Oe and an enhanced coercivity (HC) of ~800 at 10K, respectively. The observed exchange bias effect, which is associated with phase coexistence of the ferromagnetic (FM) and antiferromagnetic (AF) phases, displayed a distinctive training effect, which is probably due to a competing spin order at the boundary between the FM and AF phases.
Our results show that the exchange bias effect can be induced even in single layer films with a magnetic phase coexistence state of FM and AF phases, which may be exploited as a very simple structure for spin-valve devices. On the other hand, a Ti-terminated (001) SrTiO3(STO) substrate was prepared by the so-called Alkansas method using a combined process of etching using HCl-HNO3 acidic solution and vacuum annealing at 1000 C. A high quality La0.67Sr0.33MnO3 film was deposited on the atomically flat step terrace STO substrate by using PLD. The step-terrace LSMO film showed a slightly higher curie temperature at ~340 K than a normal LSMO, and it also exhibited uniaxial magnetic anisotropy instead of biaxial magnetic anisotropy.
Thesis Advisor: Prof. Joonghoe Dho