Angle-dependent AC susceptibility, low-field magnetoresistance and switching behaviour of La0.66Sr0.34MnO3/YSZ(001) films

Abstract

The La0.66Sr0.34MnO3 (LSMO) films with thickness 200–330 nm have been grown at 750 °C on lattice-mismatched (001)-plane oriented yttria-stabilized zirconia (YSZ) using radio frequency magnetron sputtering technique. The films demonstrated columnar growth structure characterized by coexistance of grains with the averaged diameter of about 50 nm and well defined crystallographic orientations of a pseudocubic LSMO lattice, namely, (001)LSMO[110]//(001)YSZ[100] and (110)LSMO[110;100]//(100)YSZ[100]. Alternating current (AC) magnetic susceptibility, χ(H) ∼ dM/dH, and magnetoresistance, MR(H), of the films were measured at 78 and 295 K with DC magnetic field (H) applied either in-plane or out-of-plane. Unusually sharp peaks at H = ±HSW and clearly defined switching behaviour have been indicated at 78 K in both the χ(H) and MR(H) plots. The HSW values were found to increase with the out-of-plane angle, α, according to the relationship HSW = HSW0/cosα (HSW0 = 4.0 and 1.4 kA/m at 78 and 295 K, respectively) while negligible variation of HSW has been indicated by varying direction of H in a film plane. The investigations revealed close correlation between χ(H) and low-field magnetoresistance. The observed angle-dependent peak-like χ(H) anomalies have been explained assuming magnetization reversal of the multigrain films governed by interparticle interaction and pinning of magnetic domains at grain boundaries. Unusual pit-like anomaly of the transverse biased susceptibility (TS) indicated at H = ±HSW has been explained in a framework of the TS theory developed for isolated uniaxal ferromagnetic particles assuming coexistance of grains with several fixed easy axis orientations in a film plane.