Epitaxial growth and physical properties of La_1-xCa_xMnO_3-δ thin films on MgO(001) substrates

Perovskite La_1-xCa_xMnO_3-δ (LCMO) thin films with a wide range of x, i.e., 0.0 ≤ x ≤ 0.6, were deposited on MgO(001) substrates using a pulsed laser deposition (PLD) technique, Epitaxial La_0.7Ca_0.3MnO_3-δ/MgO thin films were able to be grown under a condition such as 1.5 approx. 2.1 J/cm² of a laser fluence, 650 approx. 750°C of a substrate temperature, and 100 approx. 300 mtorr of an oxygen pressure X-ray pole figures and electron diffraction pattern showed that the LCMO films were grown epitaxially on MgO(001). Rutherford Backscattering Spectroscopy measurements investigated that the epitaxial LCMO films have compositions similar to those of targets, demonstrating the PLD is a useful technique to get films with complicated chemical compositions. Various physical properties, including resistance, R, magnetoresistance, ΔR/R(H=0) ≡ (R(H)-R(0))/R(0), and magnetization, M(T), were measured. The LCMO thin films with 0.2 ≤ × ≤ 0.5 had both semiconductor-metal and ferromagnetic ordering transitions, whose temperatures are located close to each other. These physical properties were applied in terms of the magnetic polaron model.