Increase of Operating Temperature of Magnetic Field Sensors Based on La–Sr–Mn–O Films With Mn Excess

Žurauskienė

Kersulis

et al. 2022

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The results of colossal magnetoresistance (CMR) properties of La0.83Sr0.17Mn1.21O3 (LSMO) films grown by pulsed injection MOCVD technique onto various substrates are presented. The films with thicknesses of 360 nm and 60 nm grown on AT-cut single crystal quartz, polycrystalline Al2O3, and amorphous Si/SiO2 substrates were nanostructured with column-shaped crystallites spread perpendicular to the film plane. It was found that morphology, microstructure, and magnetoresistive properties of the films strongly depend on the substrate used. The low-field MR at low temperatures (25 K) showed twice higher values (−31% at 0.7 T) for LSMO/quartz in comparison to films grown on the other substrates (−15%). This value is high in comparison to results published in literature for manganite films prepared without additional insulating oxides. The high-field MR measured up to 20 T at 80 K was also the highest for LSMO/quartz films (−56%) and demonstrated the highest sensitivity S = 0.28 V/T at B = 0.25 T (voltage supply 2.5 V), which is promising for magnetic sensor applications. It was demonstrated that Mn excess Mn/(La + Sr) = 1.21 increases the metal-insulator transition temperature of the films up to 285 K, allowing the increase in the operation temperature of magnetic sensors up to 363 K. These results allow us to fabricate CMR sensors with predetermined parameters in a wide range of magnetic fields and temperatures.

Section: Resistivity Of Nanostructured Lsmo Films: Dependence On Film Thickness and Ambient Temperaturementioning

confidence: 94%

Section: Resistivity Of Nanostructured Lsmo Films: Dependence On Film Thickness and Ambient Temperaturementioning

confidence: 94%

Section: Experimental Details 21 Film Preparationmentioning

confidence: 99%

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Nanostructured Manganite Films Grown by Pulsed Injection MOCVD: Tuning Low- and High-Field Magnetoresistive Properties for Sensors Applications

Žurauskienė

Kersulis

et al. 2022

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“…15 O 3 with Mn excess. According to [ 36 ], the magnetoresistance of films with this content at room temperature is about 30% higher compared to films with stoichiometric Mn content. Another specific feature of our experiment was the highly inhomogeneous distribution of the magnetic field in the space between pancake coil and the superconducting armature where the sensor was placed.…”

Section: Methodsmentioning

confidence: 99%

The Application of a CMR-B-Scalar Sensor for the Investigation of the Electromagnetic Acceleration of Type II Superconductors

Vertelis

Balevičius

et al. 2021

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In this paper, we investigated the behavior of a type II superconducting armature when accelerated by a pulsed magnetic field generated by a single-stage pancake coil. While conducting this investigation, we performed a numerical finite element simulation and an experimental study of the magnetic field dynamics at the edge of the pancake coil when the payload was a superconducting disc made from YBa2Cu3O7−x, cooled down to 77 K. The magnetic field measurements were performed using a CMR-B-scalar sensor, which was able to measure the absolute magnitude of the magnetic field and was specifically manufactured in order to increase the sensor’s sensitivity up to 500 mT. It was obtained that type II superconducting armatures can outperform normal metals when the launch conditions are tailored to their electromagnetic properties.

“…The sensor was made from manganite film, which exhibits a negative colossal magnetoresistance effect. Due to Mn excess, it has an increased temperature range of operation from 0 °C to 90 °C (see Žurauskienė et al [ 21 ]). The active material in the sensor was a 0.4 μm thick nanostructured La 0.82 Sr 0.18 Mn 1.15 O 3 film grown on a polycrystalline Al 2 O 3 substrate by pulsed injection metal-organic chemical vapor deposition (PI MOCVD), see Zurauskienė et al [ 22 ].…”

Section: Methodsmentioning

confidence: 99%

Magnetic Field Measurements during Magnetic Pulse Welding Using CMR-B-Scalar Sensors

Lueg‐Althoff

Hahn

et al. 2020

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The possibility of applying CMR-B-scalar sensors made from thin manganite films exhibiting the colossal magnetoresistance effect as a fast-nondestructive method for the evaluation of the quality of the magnetic pulse welding (MPW) process is investigated in this paper. This method based on magnetic field magnitude measurements in the vicinity of the tools and joining parts was tested during the electromagnetic compression and MPW of an aluminum flyer tube with a steel parent. The testing setup used for the investigation allowed the simultaneous measurement of the flyer displacement, its velocity, and the magnitude of the magnetic field close to the flyer. The experimental results and simulations showed that, during the welding of the aluminum tube with the steel parent, the maximum magnetic field in the gap between the field shaper and the flyer is achieved much earlier than the maximum of the current pulse of the coil and that the first half-wave pulse of the magnetic field has two peaks. It was also found that the time instant of the minimum between these peaks depends on the charging energy of the capacitors and is associated with the collision of the flyer with the parent. Together with the first peak maximum and its time-position, this characteristic could be an indication of the welding quality. These results were confirmed by simultaneous measurements of the flyer displacement and velocity, as well as a numerical simulation of the magnetic field dynamics. The relationship between the peculiarities of the magnetic field pulse and the quality of the welding process is discussed. It was demonstrated that the proposed method of magnetic field measurement during magnetic pulse welding in combination with subsequent peel testing could be used as a nondestructive method for the monitoring of the quality of the welding process.