Hindering the magnetic dead layer in manganites

The authors demonstrate the stability of ferromagnetic order of one unit cell thick optimally doped manganite (La0.7Ba0.3MnO3, LBMO) epitaxially grown between two layers of SrRuO3 (SRO). LBMO shows ferromagnetism even above SRO Tc. Density Functional Theory calculations help understand the reasons behind this interesting result.

By the employment of x-ray magnetic circular dichroism we show that 1 u.c. thick LBMO has a T_C value between 130K and 150K when epitaxially interfaced with two adjacent 3 u.c. thick SRO layers. This trilayer structure exhibits greatly improved ferromagnetic properties compared to a single ultra-thin film of optimally doped manganite. DFT calculations show that interfacing with SRO adjacent layers provides a 3D electronic structure to the LBMO, hindering quantum confinement effects. The strong Ru-Mn magnetic coupling also enhances LBMO T_C even when SRO is already in the paramagnetic phase. In addition, SRO favourably acts like a buffer that enables LBMO octahedral rotation close to bulk values. All these effects combined contribute to the stable ferromagnetic state for ultra-thin LBMO. The results reported here demonstrate how impactful epitaxial growth is for the physical properties of perovskite oxides and that effective engineering of the properties can be obtained by the suitable choice of the substrate and buffer layers.