Irreversible magnetic properties of nanocarbon.

Magnetization M(T, B) of powder and glassy samples containing carbon nanoparticles, not intentionally doped and doped with Ag, Au and Co, is investigated at temperatures T between - 3-300 K in magnetic fields B up to 5T. According to atomic force microscopy data, a system of carbon particles has a broad size distribution, given by the average and the maximum radii of -60 nm and - 110 nm, respectively. In low fields of B << B(K), where B(K) - 1T is the mean anisotropy field, M(T) exhibits large irreversibility or deviation of zero-field cooled and field-cooled magnetizations, which is suppressed completely at B > B(K).

Variable-range hopping conductivity of La(1 - x)Sr(x)Mn(1 - y)Fe(y)O₃.

The temperature dependence of the resistivity, ρ, of ceramic La(1 - x)Sr(x)Mn(1 - y)Fe(y)O(3) (LSMFO) samples with x = 0.3 and y = 0.03, 0.