tailieunhanh - Báo cáo hóa học: " Field Dependence of the Spin Relaxation Within a Film of Iron Oxide Nanocrystals Formed via Electrophoretic "

Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Field Dependence of the Spin Relaxation Within a Film of Iron Oxide Nanocrystals Formed via Electrophoretic | Nanoscale Res Lett 2010 5 1540-1545 DOI s11671-010-9674-2 NANO EXPRESS Field Dependence of the Spin Relaxation Within a Film of Iron Oxide Nanocrystals Formed via Electrophoretic Deposition D. W. Kavich S. A. Hasan S. V. Mahajan . Park J. H. Dickerson Received 6 May 2010 Accepted 7 June 2010 Published online 20 June 2010 The Author s 2010. This article is published with open access at Abstract The thermal relaxation of macrospins in a strongly interacting thin film of spinel-phase iron oxide nanocrystals NCs is probed by vibrating sample magnetometry VSM . Thin films are fabricated by depositing FeO Fe3O4 core-shell NCs by electrophoretic deposition EPD followed by sintering at 400 C. Sintering transforms the core-shell structure to a uniform spinel phase which effectively increases the magnetic moment per NC. Atomic force microscopy AFM confirms a large packing density and a reduced inter-particle separation in comparison with colloidal assemblies. At an applied field of 25 Oe the superparamagnetic blocking temperature is tBP 348 K which is much larger than the Neel-Brown approximation of tBP 210 K. The enhanced value of tBP is attributed to strong dipole-dipole interactions and local exchange coupling between NCs. The field dependence of the blocking temperature tBp H is characterized by a monotonically decreasing function which is in agreement with recent theoretical models of interacting macrospins. D. W. Kavich J. H. Dickerson Department of Physics and Astronomy Vanderbilt University Nashville TN 37235 USA e-mail S. A. Hasan S. V. Mahajan Interdisciplinary Graduate Program in Materials Science Vanderbilt University Nashville TN 37235 USA D. W. Kavich S. A. Hasan S. V. Mahajan J. H. Dickerson Vanderbilt Institute for Nanoscale Science and Engineering Vanderbilt University Nashville TN 37235 USA . Park National High Magnetic Field Laboratory Florida State University Tallahassee FL 32310 USA .