Low field magnetoresistance in La0.67Ca0.33MnO3 and Co3O4 combined system

Significantly enhanced low-field magnetoresistance (LFMR) and maximum dMR/dH {(dMR/dH) max } values were successfully achieved from La 0.7 Sr 0.3 MnO 3 (LSMO)-manganese oxide composite samples prepared by liquid phase sintering, compared with those of the same composites prepared by solid state reaction. For this study, pure LSMO and LSMO-manganese oxide composites with various nominal compositions of (1-x)LSMOxMn 2 O 3 (x = 0.1, 0.2, 0.3, 0.4, and 0.8) were sintered at 1450°C, above the eutectic temperature of 1430°C, for 1 h in air. The highest LFMR value of 1.28% with the highest (dMR/dH) max value of 21.1% kOe −1 was obtained from the composite sample with x = 0.3 at 290 K in 500 Oe. This enhancement of LFMR and (dMR/dH) max values is ascribed to efficient suppression of magnetic disorder at the LSMO grain boundary, by forming a characteristic LSMO-manganese eutectic structure.

Section: Methodscontrasting

confidence: 87%

Section: Introductionmentioning

confidence: 99%

Magneto-transport Properties of La_0.7Sr_0.3Mn_1+dO₃-Manganese Oxide Composites Prepared by Liquid Phase Sintering

Kim¹,

You²,

Choi³

et al. 2014

“…8. In previous studies on composite perovskites [11,[27][28][29][30][31][32][33][34], the increase in MR values at low temperatures has been attributed to grain boundary effects introduced by the dopant. Although, the mechanism of the grain boundary induced MR is not yet clear, some models have been proposed.…”

Section: Resultsmentioning

confidence: 98%

“…At a high temperature (300 K) while the x = 0.4 sample has an MR value of 18% in a 6 T magnetic field, at low temperature (10 K) the same value of MR was achieved at only 0.2 T magnetic field. In many studies, it has been concluded that low field MR is caused through spin disorder due to the tunneling process at the grain boundaries, when a magnetic field is applied the spin disorder is suppressed, resulting in a high MR, especially at a low field of 1 T [32]. For higher magnetic fields (H > 1 T) all the MR curves show a nearly linear increase with increasing magnetic field.…”

Section: Resultsmentioning

confidence: 99%

Electrical Transport and Magnetoresistance of La_0.67Ca_0.33MnO₃: Ag_x(x = 0, 0.1, 0.2, 0.3, 0.4) Composites

Gencer¹,

Pektas²,

Babur³

et al. 2012

The structural, magnetic and magnetotransport properties of La 0.67 Ca 0.33 MnO 3 : Ag x (x = 0, 0.1, 0.2, 0.3 and 0.4) composites were investigated systematically. X-ray and EDX analysis indicated that Ag is not substituted into the main La 0.67 Ca 0.33 MnO 3 phase and remains an additive to the second phase at the grain boundary. The Curie temperature first decreased from 269 K for x = 0 to 257 K for x = 0.1 and then remained nearly unchanged with increasing Ag content. For the x > 0.1 samples, a second transition temperature (T MI2 ) was observed in the resistance curves. At temperatures below 150 K, a significant enhancement in MR was observed while high temperature MR decreased with increasing Ag content. The maximum MR was observed to be 55% in the x = 0.4 sample at 10 K and a 6T magnetic field, this value is larger than that of pure La 0.67 Ca 0.33 MnO 3 (53% at 265 K and 6 T). In addition, at low fields (H < 1T), a sharp increase in the MR was observed.

“…Therefore, for the enhancement of the LFMR effect, it is very critical to control the grain boundary properties of LSMO polycrystalline samples. As such an effort, many groups have attempted to improve the LFMR effect of manganese perovskites by making a composite with insulating oxides [12][13][14][15][16][17][18]. The insulating oxides usually hinder the magnetic spin alignment near the grain boundary of manganese perovskites.…”

Section: Introductionmentioning

confidence: 99%

Enhanced Low-field Magnetoresistance of La_0.7Sr_0.3Mn_1+dO₃-Mn₃O₄Composite Films Prepared by ex-situ Solid Phase Crystallization

Kang¹,

Kim²,

Yoo³

2012

We report improved low-field magnetoresistance (LFMR) effects of the La 0.7 Sr 0.3 Mn 1+d O 3 -Mn 3 O 4 composite films with the nominal composition of La 0.7 Sr 0.3 MnO 3 (LSMO)-50 mol% Mn 3 O 4 . The composite films were fabricated by ex-situ solid phase crystallization (SPC) of amorphous films at the annealing temperature region of 900-1100 o C for 2 h in a pure oxygen atmosphere. The amorphous films were deposited on polycrystalline BaZrO 3 (poly-BZO) substrates by dc-magnetron sputtering at room temperature. The Curie temperatures (T C ) of all composite films were insignificantly altered in the range of 368-372 K. The highest LFMR value of 1.29 % in 0.5 kOe with the maximum dMR/dH value of 37.4%kOe −1 at 300 K was obtained from 900 nm-thick composite film annealed at 1100 o C. The improved LFMR properties of the composite films are attributed to effective spin-dependent scattering at the La 0.7 Sr 0.3 Mn 1+d O 3 grain boundaries sharpened by adjacent chemically compatible Mn 3 O 4 grains.