Thickness Dependent and Interfacial Magnetism in LaMnO₃ Thin Films and LaCoO₃/LaTiO₃ Heterointerfaces

Charge transfer within thin LaMnO₃ films and between LaTiO₃ and LaCoO₃ in bi- and trilayer samples grown with PLD has been studied using soft X-ray absorption, dichroism and hard X-ray photoemission. Clear signs of charge transfer are seen in both systems, yielding divalent Mn and Co. Interestigly, in the LMO system, this charge transfer is also present in films of sub-critical LMO thickness, indicating a more complex behaviour than a simple thickness-dependent potential staircase leading to self-doping of the LMO. XMCD measurements of the sub-critical thickness LMO films reveal polarisable Mn spins even for only 2 or 3 unit cells thickness, whereas robust ferromagnetism emerges in thicker films. In the LCO case, in which an LaAlO₃ spacer layer is used to eliminate polarity changes at any of the interfaces, charge transfer is driven by O2p band alignment across the interface, and the degree of charge transfer and the accompanying Co magnetic moments are controlable via the thickness of the LCO layer, and the number of LTO interfaces.