Physical properties of the giant magnetoresistive perovskite system La - Er - Ca - Mn - O

Abstract

The effect of minor changes in lattice parameters and Mn 3+ /Mn 4+ ratios on the magnetoresistive and related properties of the La-Er-Ca-Mn-O perovskite system have been investigated. The latter is found to be the more important factor in determining the magnetotransport properties of these materials. One composition has been prepared by both the standard ceramic method as well as a sol-gel technique. Although the general features of the magnetotransport properties of these two samples were very similar, the magnetic properties showed significant differences. Experimental results are explained on the basis of a spindependent mechanism which is related to lattice distortion.

Solution sol–gel processing and investigation of percolation threshold in La2/3Ca1/3MnO3:xSiO2 nanocomposite

“…All the composites show similar behavior of M as a function of T as the pure LCMO sample except for a small upturn kink at around 50 K which develops for xa0: This kink is superimposed on the general ferromagnetic type behavior. Such anomaly at around 50 K has been reported earlier in composites of LCMO with SrTiO 3 [6] as well as some substituted LCMO samples [10][11][12]. Ju and Sohn [13] have explained it on the basis of local microscopic magnetic inhomogeneities arising from the variation in the Mn oxidation state.…”

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

“…of magnitude compared to bulk LCMO. The high resistivity, low and broad transition temperatures are in agreement with the microstructural results which show the presence of nanocrystalline multi-phases [10]. An interesting feature observed in the present work is the presence of a double peak in the resistivity at ≈230 and 215 K in Cr 2 O 3 nucleated LCMO.…”

Magnetic and electronic properties of the magnetoresistive perovskites La0.67−xBixCa0.33MnO3

“…With the application of the magnetic field, Mn spins within grain boundary are aligned resulting in increased carrier mobility and decreased resistivity. Domain walls, in principle, exhibit the same type of effect as discussed in earlier papers [4,13]. Within the domain wall, spins are not parallel, but change direction slowly with respect to adjacent domains.…”

“…This may result in the simultaneous presence of canted ferromagnetic and antiferromagnetic spin structures and is believed to be the principal mechanism responsible for the GMR effect in these oxides [9][10][11][12]. It is known that small changes in composition and stoichiometry can have remarkable effects on the magnetoresistive properties of these perovskites and that it is often possible to relate this behavior to changes in the lattice properties and in the Mn>/Mn> ratio [9][10][11][12][13]. In recent work, we have investigated La-Er-Ca-Mn-O-based perovskites with small variations in erbium and calcium content [13] and La M Ca MnO perovskites with M"Er, Yb and Bi [14], in order to understand these properties.…”

“…It is known that small changes in composition and stoichiometry can have remarkable effects on the magnetoresistive properties of these perovskites and that it is often possible to relate this behavior to changes in the lattice properties and in the Mn>/Mn> ratio [9][10][11][12][13]. In recent work, we have investigated La-Er-Ca-Mn-O-based perovskites with small variations in erbium and calcium content [13] and La M Ca MnO perovskites with M"Er, Yb and Bi [14], in order to understand these properties. The Bi containing system shows a particularly high value of the Curie temperature and a substantial GMR effect.…”