Enhanced low field magnetoresistance in La_0.7Sr_0.3MnO₃/TiO₂composite

Abstract

The (1 − x) La0.7Sr0.3MnO3 + xTiO2 (x ∼ 0, 0.05, 0.10, 0.15 and 0.20) composites were prepared via a solid-state reaction process. The microstructural, magnetic and transport properties of the composites were investigated. X-ray diffraction reveals that both the compounds maintain their identities, that is, there is no evidence of reaction between the La0.7Sr0.3MnO3 and TiO2. Magnetization is observed to decrease as the TiO2 content is increased. Incorporation of a TiO2 phase into the La0.7Sr0.3MnO3 matrix lowers the metal–insulator transition temperature (Tp). An enhancement in low field magnetoresistance (LFMR) is observed at temperatures below 130 K for the composites with lower TiO2 content, namely, x = 0.05 and x = 0.10. It is argued that this improved LFMR at low temperature (T < 130 K) arises from the enhanced spin-polarized tunnelling at the grain boundaries.

Enhanced magnetoresistance in double perovskite Sr2FeMoO6 through SrMoO4 tunneling barriers

“…The values of MR at room temperature are 0.69 and 0.96% for the samples B and C, respectively. This enhanced MR even at room temperature in Sr 2 FeMoO 6 due to tunneling barriers is quite different from the manganites, in which the tunneling MR is observed only at low temperature range (<130 K) [15,24]. It may be due to high Curie temperature (T c ∼ 410 K) of Sr 2 FeMoO 6 because it is well known that the tunneling magnetoresistance, which mainly attributed to a grain boundary effect, start to increase with decreasing the temperature below T c [11].…”

“…Such a tunneling barrier can be artificially fabricated through a three layer thin film such as LSMO (half-metallic)/STO (insulating)/LSMO (half-metallic) [14]. In our previous work, we produced the tunneling barrier in the composite of CMR manganites by adding TiO 2 as second phase material [15]. Some previous studies [16][17][18][19] reported the tunneling magnetoresistance in Sr 2 FeMoO 6 through SrMoO 4 grain boundary tunneling barriers, but none has shown the microstructural evidence of formation of SrMoO 4 tunneling barriers at the grain boundaries of Sr 2 FeMoO 6 .…”

Low-field magnetoresistance of La0.7Ca0.3MnO3 perovskite synthesized by reactive milling method

“…There are two main ways to increase LFMR: (i) reducing the grain size of the ceramics would imply an increase in the LFMR [3][4][5][6][7] or (ii) creating a second phase into the ferromagnetic manganite matrix had resulted in an enhancement of the LFMR. These secondary phases include, for example, artificial boundary of the insulating oxides [8][9][10] and polymer composites [11,12].…”

Polymer functionalization with manganites

“…However, the literature is very abundant in data claiming an improved magnetoresistance as well as changes of the characteristic temperatures: Curie temperature and the metal -insulator transition temperature. By our knowledge, the first spectacular results were reported when CeO 2 diluted La 0.7 Sr 0.3 MnO 3 [15] later the whole zoology of oxides followed Al 2 O 3 [16,17], Cr 2 O 3 [18], CuO [19,20], Fe 2 O 3 [21], Fe 3 O 4 [22], MgO [23][24][25][26], Nb 2 O 5 [27], NiO [28,29], SiO 2 [30][31][32], SnO 2 [33], Sb 2 O 3 [34], Ta 2 O 5 [35], TiO 2 [36,37], V 2 O 5 [38], ZnO [39][40][41][42][43][44], ZrO 2 [45][46][47][48], and even more complex compounds like BaTiO 3 [49][50][51], SrTiO3 [52,53] have been used with the main compounds We remind also the good results reported for Ag together with La 0.7 Ca 0.3 MnO 3 [54][55][56] and La 0.7 Sr 0.3 MnO 3 [57]. In our opinion, the use of the inorganic compounds was more or less a kind of blind fishing for some a...…”