Hybrid graphene-manganite thin film structure for magnetoresistivesensor application

An increasing demand of magnetic field sensors with high sensitivity at room temperatures and
spatial resolution at micro-nanoscales has resulted in numerous investigations of physical
phenomena in advanced materials, and fabrication of novel magnetoresistive devices. In this
study the novel magnetic field sensor based on combination of a single layer graphene (SLG) and
thin nanostructured manganite La0.8Sr0.2MnO3 (LSMO) film—hybrid graphene-manganite (GM)
structure, is proposed and fabricated. The hybrid GM structure employs the properties of two
materials—SLG and LSMO—on the nanoscale level and results in the enhanced sensitivity to
magnetic field of the hybrid sensor on the macroscopic level. Such result is achieved by
designing the hybrid GM sensor in a Wheatstone half-bridge which enables to employ in the
device operation two effects of nanomaterials—large Lorentz force induced positive
magnetoresistance of graphene and colossal negative magnetoresistance of nanostructured
manganite film, and significantly increase the sensitivity S of the hybrid GM sensor in
comparison with the individual SLG and LSMO sensors: Seng=5.5 mV T⁻¹ for SLG,
14.5 mV T⁻¹ for LSMO and 20 mV T⁻¹ for hybrid GM at 0.5 T, when supply voltage was
1.249 V. The hybrid GM sensor operates in the range of (0.1–2.3) T and has lower sensitivity to
temperature variations in comparison to the manganite sensor. Moreover, it can be applied for
position sensing. The ability to control sensor’s characteristics by changing technological
conditions of the fabrication of hybrid structure and tuning the nanostructure properties of
manganite film is discussed.