Hybrid graphene-manganite thin film structure for magnetoresistive sensor application

Abstract

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: S = 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.

Room temperature Co-doped manganite/graphene sensor operating at high pulsed magnetic fields

“…The highest sensitivity 70 mV/VT of the hybrid sensor can be achieved for the case r = 0.5 in the range of 1–2 T and it is high enough at lower fields: 57 mV/VT at 0.5 T (in comparison, 12 mV/T and 40 mV/T for individual 3LG, LSMCO, respectively). These results demonstrate improvement of sensitivity of Co-doped manganite/3-layer graphene sensor in comparison with previously published results on manganite/single layer graphene sensor 20 exhibiting normalized sensitivities of 16 mV/VT at 0.5 T and 29 mV/VT at 2 T. However, at 20 T the sensitivity of the LSMCO/3LG sensor drops to 7 mV/VT for r = 0.5, respectively. It has to be noted that in the case of r = 0.1 the sensitivity of hybrid sensor is lower at low fields (20 mV/VT at 0.5 T), however, it is high enough in a wide range of magnetic fields (40 mV/VT at 2.5–7 T and 17 mV/VT at 20 T) and no saturation of the response signal was observed up to 20 T (see Fig.…”

“…However, the observed positive magnetoresistance of graphene, which is caused by Lorentz force induced Gauss effect, is small at low-field due to classical MR ~ B 2 dependence 19 . In order to overcome the mentioned problems of manganite-based MR sensors and to increase the sensitivity of graphene in low magnetic fields, a novel hybrid graphene/manganite (GM) sensor based on combination of a single layer graphene (SLG) and La 0.82 Sr 0.18 MnO 3 manganite film was recently proposed and investigated up to 2.3 T 20 . In the mentioned paper, the hybrid single layer graphene/manganite sensor showed the increased sensitivity in comparison to the individual graphene and manganite sensors.…”

Engineering of Advanced Materials for High Magnetic Field Sensing: A Review

“…A different approach was suggested for increasing the magnetoresistance and corresponding response signal of a sensor by combining into one hybrid structure a single-few-layer graphene exhibiting positive magnetoresistance and lanthanum manganite film exhibiting negative magnetoresistance [ 12 , 140 , 141 ]. Figure 19 a (1)–(3) drawings present such structure prepared on both sides of the same Al 2 O 3 substrate, which ensures the very small sensing area of the magnetic sensor [ 140 ].…”

Magnetoresistance properties in nickel-catalyzed, air-stable, uniform, and transfer-free graphene

“…For example, single-layer exfoliated graphene on terraced SrTiO 3 substrate was used to enhance the room-temperature colossal MR up to 5000% at B = 9 T [12]. Besides, an encapsulated hexagonal boron nitride (h-BN) with exfoliated monolayer graphene could elevate the room-temperature extraordinary MR to 1000% at B = 8 T [13] and be used for magnetic sensors [14,15]. Particularly, single-layer CVD graphene capped with h-BN can efficiently increase the roomtemperature MR to 140% at B = 9 T [11].…”