Abstract
The polycrystalline perovskites La2/3(Ca1−x Sr x )1/3MnO3 (x=0,0.2,0.4,0.6,0.8,1) were successfully prepared by a modified method of solid-state reactions, in which the ingredient mixture with ethanol as a liquid milling medium to form suspension was milled by high-energy ball milling for 10 h and sintered in air at 1400 °C for 10 h. The microstructure, electrical transport, and low-field magnetoresistance (LFMR) of the perovskites were investigated to study the room-temperature magnetoresistance (RTMR) behavior. The results reveal that the metal-to-insulator transition temperature (T MI) increased with increasing doping level x, and the peak values of the magnetoresistance (MR) near T MI dropped with the more Ca2+ substituted. A single-phase La2/3Ca1/3MnO3 showed T MI at 263 K and the peak MR of 23 % in the applied field of 3 kOe near T MI. The LFMR effect at room temperature could be obtained by controlling the doping Sr2+-substituted Ca2+ level. When x=0.29, transition temperature (T MI) was 305.30 K, and the MR effect was recorded up to 12.9 % at 298.55 K and 3 kOe. Finally, the possible mechanism is discussed.
Highlights
Intense researches have been carried out for the potential application of magnetic field sensor and magnetic recording, since large magnetoresistance (MR) effect was discovered in the doped manganese oxide Re1−x Ax MnO3 (Re = trivalent rare earth and A = divalent metal)
The colossal magnetoresistance (CMR) usually occurs at low temperature range and strong magnetic field, and this has become the main obstacle to the practical application
The low-field magnetoresistance (LFMR) [12,13,14,15], which is the significant MR effect that can be observed at a low magnetic field just several thousand mT or below, has been triggered renewal researches on the polycrystalline doped rare earth manganese perovskite
Summary
Intense researches have been carried out for the potential application of magnetic field sensor and magnetic recording, since large magnetoresistance (MR) effect was discovered in the doped manganese oxide Re1−x Ax MnO3 (Re = trivalent rare earth and A = divalent metal). This kind of perovskite possesses unique properties as the colossal magnetoresistance (CMR), metal-to-insulator (M-I) transition and phase separation, etc. Powders can suffer more profound milling, which was helpful for obtaining the smaller particle size and avoiding the inhomogeneity to be introduced By this method, the polycrystalline perovskites La2/3(Ca1−x Srx )1/3MnO3 (LCSMO) (x = 0, 0.2, 0.4, 0.6, 0.8, 1) were successfully synthesized. We have discussed the relation between the peak MR value, the metal-to-insulator transition temperature (TMI), and doped level of x
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