MAGNETIC-PROPERTIES OF A NEW AMORPHOUS MAGNET

An amorphous phase of Co3BTCA2(H2O)6 has been prepared (BTCA = 1,3,5-b enzenetricarboxylate). The static properties (dc susceptibility, hyste resis) of Co3BTCA2(H2O)6 are similar to those of other ''glassy'' magn etic systems, but the dynamics of Co3BTCA2(H2O)6 (absence of long rela xation times, disappearance of frequency dependence at low temperature s) are unusual. The amorphous phase is characterized by a narrow hyste resis loop at low temperature. For the hysteresis curve at 4.2 K, the coercive field is several hundred Oersted and the remnant magnetizatio n is on the order of 10(-2) M(sat). The temperature dependence of the dc magnetic susceptibility shows an unusual field dependence below 30 K, with the largest effective moments being obtained in the smallest a pplied fields. The freezing temperature, T(f), in zero field, as deter mined by both dc and ac susceptibilities, has been found to be T(f) = 23 K. The ac susceptibility shows the characteristic spin glass freque ncy dependence, yet loses all frequency dependence for temperatures be low 9 K.