Tuning the cation distribution and magnetic properties of single phase nanocrystalline Dy3Fe5O12 garnet

Abstract

Synthesizing single phase nanocrystalline rare earth iron garnet is difficult owing due to its complex crystal structure. In this report, single phase Dy3Fe5O12 nanoparticles with different grain sizes (50, 32, and 22 nm) were prepared using the ball milling technique in a controlled atmosphere. The average grain size decreases with milling time, and reaches 22 nm after 30 h of milling. The magnetization for the as-prepared micron sized Dy3Fe5O12 is in quasi-perfect agreement with the single crystal values, and all the Fe and Dy ions are in trivalent state. When the grain size is reduced below 50 nm (10 h), the magnetization strongly depends upon the applied field, and no saturation is observed even at an applied field of 280 kOe. The compensation temperature (Tcomp) for the nanocrystalline Dy3Fe5O12 samples are a few degrees higher than that of the bulk. There is no evidence for the presence of Fe2+ charge state in the as-prepared garnets. However, Mössbauer spectroscopy studies show that about 14–15 at. % Fe2+ content was found in the 30 h (22 nm) milled sample at 77 K. Oxygen vacancies created during milling induces the presence of Fe2+ ions in the nanocrystalline Dy3Fe5O12 particles.