TY - JOUR A1 - Rades, Steffi A1 - Kraemer, S. A1 - Seshadri, R. A1 - Albert, B. T1 - Size and crystallinity dependence of magnetism in nanoscale iron boride, alpha-FeB N2 - A nanoscale boride, α-FeB, with grains of variable size and crystallinity was synthesized by precipitation from solution followed by heat treatment (450 °C, 550 °C, 750 °C, 1050 °C). Analysis of transmission electron micrographs, electron diffraction, and magnetic measurements suggests superparamagnetism at room temperature for the smaller, more disordered particles of FeB, while the larger, more crystalline particles of α-FeB, with a particle size of approximately 20 nm, display open magnetic hysteresis loops and blocking. In contrast to the soft ferromagnetism of bulk β-FeB, which was synthesized by conventional solid state reaction at 1500 °C, the sample of α-FeB annealed at 1050 °C is a harder ferromagnet, possibly due to stacking faults that pin the magnetic domains; these stacking faults are apparent in the high resolution transmission electron micrographs. The changes in magnetic behavior are visible from the varying blocking temperatures (63 K, 94 K, 150 K, and >320 K from the smallest to the largest particles) and correlate with the transformations from amorphous to α-FeB and from α-FeB to β-FeB. KW - Iron KW - Boride KW - Nano KW - Magnetism KW - Electron microscopy PY - 2014 DO - https://doi.org/10.1021/cm403167a SN - 0897-4756 SN - 1520-5002 VL - 26 IS - 4 SP - 1549 EP - 1552 PB - American Chemical Society CY - Washington, DC AN - OPUS4-30288 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -