Magnetic phase profile in La0.7Ca0.3MnO3/Pr0.58Ca0.42MnO3 superlattices: Role of substrate inherent disorders

Abstract

We report the impact of dissimilar substrate inherent twinning over the structural, electrical and magnetic properties of otherwise identical ferromagnetic/antiferromagnetic La0.7Ca0.3MnO3/Pr0.58Ca0.42MnO3 (LCMO/PCMO) superlattices (SLs). 12 layers of LCMO and PCMO each ~11 nm thick were deposited and then LCMO was deposited as the top layer. The SLs were fabricated by RF magnetron sputtering method over three LaAlO3 (0 0 1) substrates embodied with different twinning disorders. Structural analysis employing high resolution X-ray diffraction (HRXRD; 2θ, ω, and ϕ scans) demonstrates that substrate twin structures exactly get imprinted over all the superlattice peaks. Transport and magnetization measurements showed coupled insulator-metal (IM)/paramagnetic-ferromagnetic (PM-FM) transition around 220 K in all the three SLs. In the high temperature PM region all the samples behave similarly however at low temperatures where long-range ferromagnetic metal (FMM) and antiferromagnetic insulating (AFMI) phases start emerging in LCMO and PCMO respectively, SLs show deviant behaviors. This is ascribed to the substrate originated microstructural disorders in SLs which are distinct for all the samples and hence perturb FMM/AFMI interfacial interactions differently. Samples with prominently large substrate FWHM = 0.683° and 0.959° respectively show a second but weak IM transition and a strong hysteretic IM transition behavior. Magnetization displays a hysteretic behavior in field cooled data measured during cooling and warming cycles. The hysteresis gets stronger with the rise in FWHM which signifies an enhancement of phase competition between FMM and AFMI phases at the interfaces. This behavior of LCMO/PCMO SLs is attributed to the interfacial exchange interactions lead magnetic reconstruction at the interfaces.