Showing papers by "S. M. Yusuf published in 2002"
TL;DR: In this article, the effects of 25 at. % Ga substitution on the Mn site in the ferromagnetic La0.67Ca0.33MnO3 perovskite (TC=265 K) have been studied by ac susceptibility, dc magnetization, neutron-diffraction (ND) and neutron-depolarization (NDP) techniques.
Abstract: The effects of 25 at. % Ga substitution on the Mn site in the ferromagnetic La0.67Ca0.33MnO3 perovskite (TC=265 K)have been studied by ac susceptibility, dc magnetization, neutron-diffraction (ND) and neutron-depolarization (NDP) techniques. The ND study shows a complete absence of long-range magnetic ordering in the substituted sample. However, the presence of spin clusters (with net moments) at T 48 K. A temperature-independent cluster size and moment are prominent at T ≲ 30 K Above 30 K (blocking temperature), superparamagnetic relaxation is evident
4 citations
TL;DR: In this article, the low frequency data was analyzed using Summerfield scaling theory for hopping conductivity, and the scaling behavior has significantly different values in the conducting and insulating regimes.
Abstract: ac Conductivity measurements are carried out across the metal to insulator transition in NiAl0.7Cr0.7Fe0.6O4. The low frequency data is analyzed using Summerfield scaling theory for hopping conductivity. The exponent of the scaling behavior has significantly different values in the conducting and insulating regimes. The hopping frequency and the zero frequency conductivity are found to increase with temperature, slowly in the metallic regime and rapidly in the insulating regime.
3 citations