Paper AC+MI+SA-WeM13
Insights into the Magnetic Dead Layer in La_0.7Sr_0.3MnO₃ Thin Films from Temperature, Magnetic Field and Thickness Dependence of their Magnetization

Wednesday, October 24, 2018, 12:00 pm, Room 202C

Detailed dc magnetization (M) measurements of a 7.6 nm La_0.7Sr_0.3MnO₃ thin film samples is investigated. The sample was fabricated by pulsed laser deposition. Zero-field-cooled (ZFC) M vs. applied field (H) cooled down to T = 5 K reveal the presence of negative remanent magnetization (NRM) as well as in ZFC M vs. temperature (T) measurements in H = 50 Oe and 100 Oe. ZFC and FC (field-cooled) protocols are used to determine the blocking temperature T_B in different H. Isothermal hysteresis loops at different T are used to determine the temperature dependence of saturation magnetization (M_S), remanence (M_R) and coercivity H_C. The M_S vs. T data are fit to the Bloch law, M_S (T) = M₀ (1 – BT^3/2), showing a good fit for T < 100 K and yielding the nearest-neighbor exchange constant J/k_B ≅ 18 K. The variations of T_B vs. H and H_C vs. T are well described by the model often used for randomly oriented magnetic nanoparticles with magnetic domain diameter ≈ 9 nm present in the dead-layer of thickness d =1.4 nm. Finally, the data available from literature on the thickness (D) variation of Curie temperature (T_C) and M_S of LSMO films grown under 200, 150, and 0.38 mTorr pressures of O₂ are analyzed in terms of the finite-size scaling, with M_S vs. D data fit to M_S (D) = M_S(b)(1-d/D) yielding the dead layer thickness d = 1.1 nm, 1.4nm and 2.4 nm respectively.