Magnetic and transport properties of polycrystallineLa0.7Sr0.3Mn

Abstract

The effect of Fe doping (р10%) on polycrystalline samples of La 0.7 Sr 0.3 MnO 3 has been studied by means of x-ray diffraction, resistivity, ac susceptibility, magnetization, and magnetoresistance measurements. Fe doping does not affect the lattice structure, but it weakens the ferromagnetism and substantially augments the resistivity of the samples. The magnetoresistance of a sample with 10% Fe doping, in a 5 T magnetic field, was 4 times greater than that of the undoped sample near the peak in the resistivity. The results were explained in terms of the formation of antiferromagnetic clusters of Fe ions. At 5 K the magnetoresistance showed no significant dependence on Fe doping, but it displayed large variations in fields below 0.5 T for all samples. This behavior was attributed to spin-polarized tunneling at the grain boundaries of the polycrystalline samples. A variable-range hopping behavior in the resistivity was also encountered in all the samples at low temperatures.

Interplay between double-exchange, superexchange, and Lifshitz localization in doped manganites

“…Some experimental work has already been done for these materials, [12][13][14][15][16] but from the present analysis we believe that several interesting features have not still been found experimentally. Specifically, we will show that, from the knowledge gained in the study of the phase diagrams of (La 1Ϫz RE z ) 1Ϫx Sr x MnO 3 and (La 1Ϫz RE z ) 1Ϫx Ca x MnO 3 , where RE is a trivalent rare earth, and from our model calculations, one can conclude that:…”

“…Therefore it is a challenge to this model to give account of the experimental situation of the double series ͑1͒ in the range 0.3ϽxϽ0.5, [12][13][14][15][16] without stretching out the values of J AF already determined. 21,22,24 Ϫ1 with respect to the case y ϭ0.…”

Structural, magnetic and electrical transport properties for a series of La1−xSrxFe1−xMnxO3 (0.3≤x≤0.7) compounds

“…Takeuchi et al [16] suggested that Fe substitution for Mn dilutes the DE mechanism and shows typical spin glass and insulating behaviors. Several authors reported that Fe and Mn shows anti-ferromagnetic interaction in the Ln 1−x A x Mn 1−y Fe y O 3 compounds under the conditions of y ≤ x [17][18][19].…”

Magnetic properties and colossal magnetoresistance of La5/6Na1/6Mn1−yFeyO3 with 0≤y≤0.10

“…Mn site doping effects with transition elements have been extensively investigated [12,13]. The effects of substitution on the Mn site by other transition element is further known to affect the properties due to the changes produced in the average electron concentration and the shifts in the position of the e g and t g sub-bands.…”