Toward ultrathin ferromagnetic metal of (110) La2/3Sr1/3MnO3 thin films

Abstract

The ferromagnetic metal La2/3Sr1/3MnO3 (LSMO) is an important correlated oxide material for oxide spintronics. However, the existence of a dead layer not only degrades device performance but also hinders the ultimate miniaturization of devices. Intense research has been made to eliminate the dead layer and understand its origin. Here, we have investigated the dead layer of (110)-oriented LSMO films on SrTiO3 (STO) substrates in which there is no polar discontinuity across the interface, in contrast to the (001)-oriented LSMO/STO interface. Our results reveal an 8 unit cell (u.c.) dead layer for (110) LSMO. Angle resolved x-ray photoemission demonstrating Sr segregation at the surface. Additionally, the broken symmetry at LSMO/vacuum interfaces also degrades the transport property. By introducing a capping layer, the film conductivity is enhanced. Finally, an ultrathin limit dead layer of 5 u.c. (=1.36 nm) has been obtained by introducing both the LaMnO3 capping layer and the buffer layer to compensate the excess holes at both LSMO/STO and Vacuum/LSMO interfaces and also to reduce the structural distortion at the top surface of LSMO. Our work paves the way toward eliminating the LSMO dead layer for spintronics application and provides a route to engineer the intriguing physical properties of oxide heterointerfaces.