Sublattice Magnetic Relaxation in Rare Earth Iron Garnets

The magnetic properties of rare earth garnets make them attractive materials for applications ranging from optical communications to magnetic refrigeration. The purpose of this research was to determine the AC magnetic properties of several rare earth garnets, in order to ascertain the contributions of various sublattices. Gd3Fe5O12, Gd3Ga5O12, Tb3Fe5O12, Tb3Ga5O12, and Y3Fe5O12 were synthesized by a solid state reaction of their oxides and verified by x-ray diffraction. Frequency-dependent AC susceptibility and DC magnetization were measured versus temperature (10-340 K). Field cooling had little effect on AC susceptibility but had a large effect on DC magnetization, increasing magnetization at the lowest temperature and shifting the compensation point to lower temperatures. Data suggest that interaction between the two iron sublattices result in the two frequency dependent magnetic relaxations in the iron garnets, which were modeled using the Vogel-Fulcher law.