Evidence for magnetic phase separation in La_0.86Sr_0.14Mn_1−xCu_xO_3+δmanganites from NMR and magnetic measurements

Abstract

Polycrystalline La0.86Sr0.14Mn1−xCuxO3+δ (x = 0, 0.05, 0.10, 0.15, 0.20) manganites were investigated by means of magnetic measurements and zero-field 139La and 55Mn nuclear magnetic resonance (NMR) spectroscopy. Magnetization versus temperature measurements revealed a paramagnetic to ferromagnetic transition in most samples, with lower Curie temperatures and broader transitions for samples with higher Cu contents. The details of the magnetization measurements suggested a phase-separated scenario, with ferromagnetic clusters embedded in an antiferromagnetic matrix, especially for the samples with large Cu contents (x = 0.15 and 0.20). Zero-field 139La NMR measurements confirmed this finding, since the spectral features remained almost unchanged for all Cu-doped samples, whereas the bulk magnetization was drastically reduced with increasing Cu content. 55Mn NMR spectra were again typical of ferromagnetic regions, with a broadening of the resonance line caused by the disorder introduced by the Cu doping. The results indicate a coexistence of different magnetic phases in the manganites studied, with the addition of Cu contributing to the weakening of the double-exchange interaction in most parts of the material.

Effect of Pr doping on the properties of Bi0.5−xPrxCa0.5MnO3 (0≤x≤0.50) manganites

“…This coupling is caused by several parameters like disorder in the sample [11], applied pressure [12,13] or applied magnetic and electric field [14,15] and the grain size of the sample [16][17][18][19]. The coupling can be altered by different types of substitutions at A-site [20][21][22] and Bsite [23][24][25], which introduce disorder in the system and in turn affects the crystal structure and properties. The trivalent rare-earth ions doping leads to evolution of different co-existing magnetic phases such as paramagnetic (PM), ferromagnetic (FM), anitferromagnetic (AFM) and…”

“…The phase separation (PS) phenomenon has been proposed to explain the effect of doping on the properties of manganites [19,25,[28][29][30]. The PS can be electronic or structural.…”