Magnetic Susceptibility of Pressed Powders of Some Rare-Earth Iron Garnets

Abstract

The molar magnetic susceptibilities (χ_м) of spherical balls of rare-earth iron garnets REIG's, with RE = Y, Gd, Dy, Ho, Er and Yb, prepared from pellets pressed at pressures ranging from 2 to 8 × 107 kg m^-2 , have been measured in the temperature range 300-900 K. It is found that χ_мα exp( - f), where f is the pore fraction of the pressed balls. It has also been observed that χ_м for a particular garnet at a fixed temperature increases from powder through pressed material to single crystal. REIG's reveal typical ferrimagnetic behaviour with the ferrimagnetic Curie temperature (T_c) lying in the range 550-570 K for single crystals. In general, for pressed material T_c increases linearly with density. The χ_м^-1 vs, T variation has been analysed using molecular field theory. It has been found that for T ≫ T_c the magnetic ions behave as if they were almost free and yield a magneton number very close to their free ion value.