Enhancement of Room-Temperature Low-Field Magnetoresistance in Nanostructured Lanthanum Manganite Films for Magnetic Sensor Applications

Abstract

The results of colossal magnetoresistance (CMR) properties of La1-xSrxMnyO3 (LSMO) films grown by the pulsed injection MOCVD technique onto an Al2O3 substrate are presented. The grown films with different Sr (0.05 ≤ x ≤ 0.3) and Mn excess (y > 1) concentrations were nanostructured with vertically aligned column-shaped crystallites spread perpendicular to the film plane. It was found that microstructure, resistivity, and magnetoresistive properties of the films strongly depend on the strontium and manganese concentration. All films (including low Sr content) exhibit a metal–insulator transition typical for manganites at a certain temperature, Tm. The Tm vs. Sr content dependence for films with a constant Mn amount has maxima that shift to lower Sr values with the increase in Mn excess in the films. Moreover, the higher the Mn excess concentration in the films, the higher the Tm value obtained. The highest Tm values (270 K) were observed for nanostructured LSMO films with x = 0.17–0.18 and y = 1.15, while the highest low-field magnetoresistance (0.8% at 50 mT) at room temperature (290 K) was achieved for x = 0.3 and y = 1.15. The obtained low-field MR values were relatively high in comparison to those published in the literature results for lanthanum manganite films prepared without additional insulating oxide phases. It can be caused by high Curie temperature (383 K), high saturation magnetization at room temperature (870 emu/cm3), and relatively thin grain boundaries. The obtained results allow to fabricate CMR sensors for low magnetic field measurement at room temperature.

Investigation on the structural, magnetic, magnetocaloric and magnetotransport behaviour of La0.7Sr0.3MnO3 manganites synthesised by different routes

“…71 The linear plot of ln(ÀDS M ) vs. ln(H) at T C is depicted in Fig. 12(a) and (b), respectively, for samples L1 and L2, which in turn provides the value of n. For L1 and L2, respectively, the derived values of n are 0.748(8) and 0.797 (2). Critical exponents are established using…”

“…CMR materials have attracted significant interest in recent years due to their potential application in sensors and magnetic memory devices. 2,3 Manganites have also been found to exhibit a large MCE under moderate applied fields, revealing that CMR manganites are also possible candidates for magnetic refrigeration applications. Magnetocaloric materials offer an environmentally sound and economically viable refrigeration technology as an alternative to the traditional vapour compression-expansion cycle, leading to the development of effective green cooling systems completely for both domestic and industrial applications.…”

“…Transition metal oxides display a staggeringly wide range of physical phenomena, such as multiferroicity, 1 colossal magnetoresistance (CMR), 2–7 high temperature superconductivity, 8,9 and magnetocaloric effect (MCE), 10–12 as cathode materials in solid oxide fuel cells 13 and can have unique applications in spintronics 14,15 as well as in hyperthermia applications. 16 Perovskite manganese oxides of the form R 1− x A x MnO 3 (R = trivalent rare earth ion, A = divalent alkaline earth ion) have received wide attention recently due to their exceptional magnetic and electrical characteristics and the close proximity between their spin, charge, orbital, and lattice degrees of freedom.…”

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

“…It was demonstrated that for single-layer polycrystalline La 0.83 Sr 0.17 Mn 1.21 O 3 films grown on quartz substrate, the LFMR at 25 K showed twice higher values (31% at 0.7 T, see Figure 7 c) in comparison to films grown on polycrystalline Al 2 O 3 or SiO 2 substrates (~15%) (see Figure 7 d,e, respectively) [ 68 ]. Recently, it was demonstrated that Mn excess ( y > 1) in polycrystalline La 1−x Sr x Mn y O 3 (LSMO) films increases the Curie temperature what results in LFMR effect at close to room temperatures [ 69 ]. It was found that the magnetoresistance of (–1.23 ÷ –0.8)% at temperatures (250 ÷ 290) K could be achieved at a magnetic field of 50 mT for La 0.7 Sr 0.3 Mn 1.15 O 3 films without the introduction of an additional insulating phase, only by the adjustment of the chemical composition and film growth conditions (see Figure 7 f).…”

“…Measurements performed at ambient temperature of 25 K. Reprinted from [ 68 ], copyright 2022 MDPI; and ( f ) MR vs. magnetic field dependences at room temperature for nanostructured La 1−x Sr x Mn y O 3 films with different Sr content x and constant Mn excess y = 1.15. Reprinted from [ 69 ], copyright 2022 MDPI.…”