Magnetism and nonlinear charge transport in NiFe2O4/{\gamma}-Al2O3/SrTiO3 heterostructure: Toward Spintronic Applications

Abstract

We present the synthesis and study of the magnetic and electronic properties of NiFe2O4/{\gamma}-Al2O3/SrTiO3 heterostructure. The {\gamma}-Al2O3/SrTiO3 interface hosts a high-mobility two-dimensional electron gas (2DEG) with large spin-orbit coupling, making it promising for spintronics applications if it can be coupled to a suitable source of spin currents. Here, we synthesize a ferrimagnetic insulating NiFe2O4(001) layer on {\gamma}-Al2O3(001)/SrTiO3(001) using a low-temperature reactive sputtering at 150 deg C without compromising the mobility and charge carrier density of the 2DEG at the {\gamma}-Al2O3(001)/SrTiO3(001) interface. The sheet resistance of both {\gamma}-Al2O3/SrTiO3 and NiFe2O4/{\gamma}-Al2O3/SrTiO3 exhibits metallic behavior down to cryogenic temperatures, with a low temperature upturn driven by the Kondo-like scattering. Most importantly, NiFe2O4/{\gamma}-Al2O3/SrTiO3 behaves as a magnetic diode at low temperatures, and its rectification performance increases significantly with increasing magnetic field strength giving rise to a robust magneto-electronic rectification effect at low temperatures, which provides a first step towards the development of all-oxide heterostructures capable of efficient spin-charge conversion.