2010/11/10 by Wiqar Hussain Shah, Shah, Wiqar Hussain
Materials Science · #Magnetic and transport properties of perovskites and related materials
paper · pdf · doi:10.48550/arxiv.1011.2286
We have studied the magnetic and transport behavior of doped La0.65 A0.35\nMn0.95Fe0.05 O3 (A= Ca, Sr, Pb, Ba) compounds. All the compositions show\nferromagnetic/metal to paramagnetic/insulator transition except the Pb doped\nsample which is insulating and ferromagnetic in the entire temperature range.\nThe simultaneous occurrence of ferromagnetism and insulating behavior in Pb\ndoped compound is most likely due to the presence of FM clusters separated by\nFe and Mn ions that are coupled AFM and hence prevent the current from crossing\nthe inter-domain region. The magnetization and Tc are decreased by decreasing\nthe Cation size on La site. We observed that (for a fixed Fe content of 5%) the\ntransition temperature and magnetic moment at 77 K is a maximum for Sr doped\nsample and is decreasing if we increase or decrease the cation size from Sr\nsize. The maximum value of Tc and magnetic moment for Sr based sample is most\nlikely due to the closer ionic sizes of La and Sr as compared to the other\ndopants (Ca, Pb, Ba). The decrease in the transition temperature and magnetic\nmoment is due to the deviation of Mn-O-Mn angle from 1800 caused by the size\nmismatch of the A site cations. This deviation leads to weakening of the FM\ndouble exchange (DE). We observed a spin freezing type effect in the Pb doped\nsample below 120 K in resistivity, AC susceptibility and in magnetization. This\nsuggests that the AFM interactions introduced by the Fe are most effective in\nthe Pb doped composition leading to increased competition between the FM and\nAFM interactions. This FM and AFM interaction generates some degree of\nfrustration leading to the appearance of spin glass like phase whose typical\nmagnetic behavior is studied for small ion when the metallic like behavior is\nlost.\n