Enhanced intergrain tunneling magnetoresistance in double perovskite Sr2FeMoO6 polycrystals with nanometer-scale particles

Abstract

Polycrystalline ordered double perovskite Sr2FeMoO6 bulk samples with grain size in the range of 29–45 nm have been synthesized at temperatures from 900 to 1000 °C, using a sol-gel method. We find that the intergrain magnetoresistance is closely correlated with the grain size. The sample with the grain size of 29 nm shows large magnetoresistance Δρ/ρ0, 30%–20% at a low magnetic field of 4 kG over a wide temperature range from 20 to 300 K. The results can be explained in terms of spin-dependent intergrain tunneling model.

Enhancement in Curie temperature and reduction in magnetoresistance of Sr2(Fe1−xNix)MoO6 (0≤x≤0.15)

“…The large LFMR of SFMO, which is believed to be rooted in the spin dependent scattering at the grain boundary, can be achieved by modulating the grain boundaries in SFMO [7][8][9]. In addition, LFMR has been found to be enhanced by doping at the Fe site [10].…”

Preparation of magneto-resistive Sr2FeMoO6 through molybdic acid gelation

“…This may be due to a volatilization of the Sr amorphous component from the grain boundary of the sintered pellet. Some papers have reported higher MR ratio of 10-20% by other sol-gel method [3,5]. Much smaller amount of impurities and/or higher Fe/Mo ordering might be achieved in their products.…”

“…There are several advantages on sol-gel method; homogeneous mixing can be attained in relatively low temperature, and small grain size can be expected on the products and so on. Some papers reported high MR ratio in 10-20% for Sr 2 FeMoO 6 prepared by sol-gel method [3,5]. Both Fe/Mo ordering and impurity amount can be expected to be very important for MR effect as well as grain size on polycrystalline Sr 2 FeMoO 6 .…”

“…Band calculations indicated Sr 2 FeMoO 6 had a half-metallic electronic state and its MR has been assumed to be dominated by spin-polarized tunneling through insulating grain boundaries [1,2]. Its smaller grain size leads to larger MR effect at low applied field [3]. Solid state reaction at high temperature has been applied to prepare Sr 2 FeMoO 6 with large grain size [4].…”

Modern routes for materials rapid processing

“…The Sr 2 FeMoO 6 (SFMO) double perovskite is very attractive due to the appreciable low-field magnetoresistance in granular form and a relatively high Curie temperature (410-450 K) [4][5][6][7][8]. Taking into account very weak values of magnetoresistance in single crystals, the role of grain boundaries has been extensively studied [9][10][11][12][13].…”