MAGNETIC PROPERTIES OF NANOSCALE RARE-EARTH GARNETS (RIG) R=Dy, Tb GROUND PARTICLES NEAR THE COMPENSATION TEMPERATURE

摘要

Ferrimagnetic garnets, with or without substitutions, are potential materials for magneto-optical applications because their Faraday rotation is large and they operate with blue-green radiation. In addition to yttrium iron garnet (YIG) the properties of rare-earth iron garnets are worthy of investigation. In this current work, the starting point is a large stoichiometric single crystal(s) of RIG (R=Dy or Tb) that were made by the flux technique. These crystals were then ground in a high-energy ball mill with both chamber and ball made of silicon nitride, thus eliminating the possibility of contamination when stainless-steel is used. Grinding times of up to 50 hours led to particles that were as small as 5-10 nm. The magnetization was measured in fields up to 9.0 Teslas and at temperatures between 4 and 300 K. Although a broad minimum is observed, the magnetization does not go to zero. As expected for nanometer particles the magnetization is significantly lower than for the bulk even in fields of up to 9 T. On the other hand, Moess-bauer spectra in longitudinal magnetic fields (the gamma-ray direction is parallel to the applied field) clearly delineates the magnetic compensation temperature T_c. It is relatively sharp and agrees well with earlier measurements made on the same crystals. There is no change in the ~(57)Fe hyperfine field at T_c.