Enhanced magnetoresistance in sintered granular manganite/insulator systems

Abstract

We report significant enhancements of magnetoresistance in granular (La0.67Ca0.33MnO3)x/(SrTiO3)1−x. The system exhibits a conduction threshold at x=xc∼60%, around which magnetoresistance versus x has a maximum. The composition xc at which maximum enhancement in magnetoresistance is observed is the same at high (around 5 T) and at low (a few hundred Oersted) fields. The enhancement is consistent with the disorder-driven amplification of spin-dependent transport at the structural boundaries of the mixture.

Enhanced low field magnetoresistive response in (La2/3Sr1/3MnO3)x/(CeO2)1−x composite thick films prepared by screen printing

“…It is found that the conductivity, G, decrease as Gϰe x , as typically found in other percolating systems. 18 The RT magnetoresistance of the sample with xϭ1 and in the H ʈ geometry is shown in Fig. 5.…”

“…One of the routes used is the reduction of the conduction path by diluting LSMO powders with a magnetic insulator ͑MI͒ 9,10 or a nonmagnetic insulator ͑NMI͒. 11,12 In fact, LFMR responses obtained in diluted LSMO/NMI composites have demonstrated to be adequate for some technological applications, such as potentiometers, position sensors, etc. 2 From the technological point of view to develop competitive low cost magnetic sensors, based on the LFMR response of manganite materials, involves two different aspects:…”

Large magnetoresistance in (La1−xCaxMnO3)1−y:ZrO2 composite

“…Attempts have also been made to increase the MR through the formation of some composites. [9][10][11] Recently our work on La 0.67 Ca 0.33 MnO 3 ͑LCMO͒:SiO 2 composite 11 showed interesting results. The composite showed a percolation threshold composition corresponding to 90 vol % of LCMO, beyond which the resistivity shoots up sharply to almost 6 orders of magnitude.…”

Structure and properties of La–Ca–Mn–O composites prepared by the glass-ceramic method

“…The presence of non-magnetic insulating phase should also result in a variation of the electrical transport behavior, since the samples now consist of manganite/insulator mixture. Petrov et al [5] found the room temperature resistivity of LCMO/SrTiO 3 manganite/insulator mixture increases by about four orders of magnitude to ∼10 2 m when the LCMO fraction decreases to <0.3. The room temperature resistivity in the present work is found to be in the range 10 1 -10 2 m, clearly supporting the magnetization results of manganite phase dilution and also in agreement with the results of Petrov et al…”

“…They find that the resistivity increases with increasing Cr and exhibits a double peak behavior for Cr ≤ 0.2. The MR, however, reaches a value of only 40% in fields as high as 6.0 T. Petrov et al [5] find that the MR is greatly enhanced when La 0.67 Ca 0.33 MnO 3 (LCMO) is mixed with a non-magnetic insulator, such as SrTiO 3 . The MR exhibits a peak at a conduction threshold of 60% LCMO.…”