Thickness dependence of the magnetic anisotropy in La2/3Ca1/3MnO3 thin films grown on LaAlO3 substrates

Magnetic anisotropy of sputtered epitaxial La2/3Ca1/3MnO3 (LCMO) thin films grown on top of LaAlO3 (LAO) substrates has been studied as a function of thickness. A series of films with thickness ranging from 20 to 150 nm have been prepared. LCMO films grown on LAO substrates are subjected to an in-plane biaxial compressive strain that progressively relaxes as film thickness increases as deduced from the variation of the c cell parameter. Nevertheless, some strain is observed even in 150-nm-thick films. The relaxation process is accompanied by an improvement of the magnetic and transport properties approaching that of the bulk material. The observed magnetic easy axis evolves from perpendicular to plane for thin films towards in plane as film thickness increases. Values of the effective anisotropy constant of K1eff≈2.2×107 erg/cm3, at T=10 K, and magnetostriction constant of λ≈2×10−4 are found.