Compact manganite-graphene magnetoresistive sensor

Abstract

A magnetic field sensor based on a manganite/Al 2 O 3 -substrate/three-layer graphene structure operating in the range of 0.1–20 T was designed and fabricated. The La 0.9 Sr 0.1 Mn 1.2 O 3 (LSMO) manganite film and graphene layers were prepared on the opposite sides of polycrystalline Al 2 O 3 substrate, which enabled scaling of the effective volume of the device to about 0.16 mm 3 . The combination of two materials—graphene with positive magnetoresistance (MR) and manganite with negative MR—led to a significant increase of the response signal and sensitivity compared with individual graphene or manganite sensors. This was achieved by increasing the MR of the individual manganite and graphene elements. The MR of LSMO was increased by using pulsed-injection metal-organic chemical vapor deposition based on two precursor sources with tunable vapor supersaturation and growth rate. The MR of three-layer graphene was optimized by changing the width/length ratio of the rectangular planar configuration and scaling the dimensions from millimeters to few hundred micrometers. The result was a maximal sensitivity of 72 mV/VT in the field range of 1–3 T.